Mailing List Archive: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev

[syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 26, 2024, 5:00 AM

Post #1 of 10 (28 views)

Hello,

syzbot found the following issue on:

HEAD commit: e33c4963bf53 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16f9787b180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11655ed8980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12499380980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e06aabc50597/disk-e33c4963.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ac50f00a131e/vmlinux-e33c4963.xz
kernel image: https://storage.googleapis.com/syzbot-assets/21fd2a443e16/bzImage-e33c4963.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9a3efbc77ff7/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5d34cc6474499a5ff516@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
Read of size 8 at addr ffff888076eed7c8 by task syz-executor427/5079

CPU: 0 PID: 5079 Comm: syz-executor427 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add include/linux/list.h:169 [inline]
chrdev_open+0x2a9/0x630 fs/char_dev.c:396
do_dentry_open+0x907/0x15a0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x2860/0x3240 fs/namei.c:3799
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f722cb71329
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff23332778 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f722cb71329
RDX: 0000000000000000 RSI: 0000000020002140 RDI: ffffffffffffff9c
RBP: 0000000000000000 R08: 00007fff233327b0 R09: 00007fff233327b0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff2333279c
R13: 0000000000000001 R14: 431bde82d7b634db R15: 00007fff233327d0
</TASK>

Allocated by task 5077:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_lru+0x178/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_mknod+0x41/0x60 fs/ntfs3/namei.c:128
vfs_mknod+0x36d/0x3b0 fs/namei.c:4001
do_mknodat+0x3ec/0x5b0
__do_sys_mknodat fs/namei.c:4079 [inline]
__se_sys_mknodat fs/namei.c:4076 [inline]
__x64_sys_mknodat+0xa9/0xc0 fs/namei.c:4076
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 0:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x10b/0x2c0 mm/slub.c:4344
rcu_do_batch kernel/rcu/tree.c:2196 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2471
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:2734 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:2838
__dentry_kill+0x20d/0x630 fs/dcache.c:603
shrink_kill+0xa9/0x2c0 fs/dcache.c:1048
shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1075
shrink_dcache_parent+0xcb/0x3b0
do_one_tree+0x23/0xe0 fs/dcache.c:1538
shrink_dcache_for_umount+0x7d/0x130 fs/dcache.c:1555
generic_shutdown_super+0x6a/0x2d0 fs/super.c:619
kill_block_super+0x44/0x90 fs/super.c:1675
ntfs3_kill_sb+0x44/0x1b0 fs/ntfs3/super.c:1785
deactivate_locked_super+0xc4/0x130 fs/super.c:472
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
ptrace_notify+0x2d2/0x380 kernel/signal.c:2404
ptrace_report_syscall include/linux/ptrace.h:415 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
syscall_exit_work+0xc6/0x190 kernel/entry/common.c:173
syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
syscall_exit_to_user_mode+0x273/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888076eed120
which belongs to the cache ntfs_inode_cache of size 1760
The buggy address is located 1704 bytes inside of
freed 1760-byte region [.ffff888076eed120, ffff888076eed800)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x76ee8
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff80000000840(slab|head|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000840 ffff888019777dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000110011 00000001ffffffff 0000000000000000
head: 00fff80000000840 ffff888019777dc0 dead000000000122 0000000000000000
head: 0000000000000000 0000000000110011 00000001ffffffff 0000000000000000
head: 00fff80000000003 ffffea0001dbba01 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0xd2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE), pid 5077, tgid 1360935967 (syz-executor427), ts 5077, free_ts 25749663853
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
__alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2175
allocate_slab mm/slub.c:2338 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2391
___slab_alloc+0xc73/0x1260 mm/slub.c:3525
__slab_alloc mm/slub.c:3610 [inline]
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
kmem_cache_alloc_lru+0x253/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
iget5_locked+0xa4/0x280 fs/inode.c:1235
ntfs_iget5+0xc7/0x3b70 fs/ntfs3/inode.c:525
ntfs_fill_super+0x2f01/0x49c0 fs/ntfs3/super.c:1300
get_tree_bdev+0x3f7/0x570 fs/super.c:1614
vfs_get_tree+0x90/0x2a0 fs/super.c:1779
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
page last free pid 1 tgid 1 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
free_contig_range+0x9e/0x160 mm/page_alloc.c:6572
destroy_args+0x8a/0x890 mm/debug_vm_pgtable.c:1036
debug_vm_pgtable+0x4be/0x550 mm/debug_vm_pgtable.c:1416
do_one_initcall+0x248/0x880 init/main.c:1245
do_initcall_level+0x157/0x210 init/main.c:1307
do_initcalls+0x3f/0x80 init/main.c:1323
kernel_init_freeable+0x435/0x5d0 init/main.c:1555
kernel_init+0x1d/0x2b0 init/main.c:1444
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
ffff888076eed680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888076eed700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888076eed780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888076eed800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888076eed880: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 26, 2024, 1:57 PM

Post #2 of 10 (28 views)

Permalink

syzbot has bisected this issue to:

commit ef9297007e9904588682699e618c56401f61d1c2
Author: Kari Argillander <kari.argillander@gmail.com>
Date: Thu Sep 2 15:40:49 2021 +0000

fs/ntfs3: Make binary search to search smaller chunks in beginning

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=144f18b0980000
start commit: e33c4963bf53 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=164f18b0980000
console output: https://syzkaller.appspot.com/x/log.txt?x=124f18b0980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11655ed8980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12499380980000

Reported-by: syzbot+5d34cc6474499a5ff516@syzkaller.appspotmail.com
Fixes: ef9297007e99 ("fs/ntfs3: Make binary search to search smaller chunks in beginning")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

hdanton at sina

Apr 26, 2024, 7:06 PM

Post #3 of 10 (26 views)

Permalink

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 26, 2024, 7:58 PM

Post #4 of 10 (26 views)

Permalink

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in chrdev_open

loop0: detected capacity change from 0 to 4096
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
Read of size 8 at addr ffff888065670e08 by task syz-executor.0/5500

CPU: 1 PID: 5500 Comm: syz-executor.0 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add include/linux/list.h:169 [inline]
chrdev_open+0x2a9/0x630 fs/char_dev.c:396
do_dentry_open+0x907/0x15a0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x2915/0x3350 fs/namei.c:3800
do_filp_open+0x235/0x490 fs/namei.c:3829
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8392c7dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8393a480c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f8392dabf80 RCX: 00007f8392c7dea9
RDX: 0000000000000000 RSI: 0000000020002140 RDI: ffffffffffffff9c
RBP: 00007f8392cca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f8392dabf80 R15: 00007ffea989b878
</TASK>

Allocated by task 5490:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_lru+0x178/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_mknod+0x41/0x60 fs/ntfs3/namei.c:128
vfs_mknod+0x36d/0x3b0 fs/namei.c:4004
do_mknodat+0x3ec/0x5b0
__do_sys_mknodat fs/namei.c:4082 [inline]
__se_sys_mknodat fs/namei.c:4079 [inline]
__x64_sys_mknodat+0xa9/0xc0 fs/namei.c:4079
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 15:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x10b/0x2c0 mm/slub.c:4344
rcu_do_batch kernel/rcu/tree.c:2196 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2471
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:2734 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:2838
__dentry_kill+0x20d/0x630 fs/dcache.c:603
shrink_kill+0xa9/0x2c0 fs/dcache.c:1048
shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1075
shrink_dcache_parent+0xcb/0x3b0
do_one_tree+0x23/0xe0 fs/dcache.c:1538
shrink_dcache_for_umount+0x7d/0x130 fs/dcache.c:1555
generic_shutdown_super+0x6a/0x2d0 fs/super.c:619
kill_block_super+0x44/0x90 fs/super.c:1675
ntfs3_kill_sb+0x44/0x1b0 fs/ntfs3/super.c:1785
deactivate_locked_super+0xc4/0x130 fs/super.c:472
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888065670760
which belongs to the cache ntfs_inode_cache of size 1760
The buggy address is located 1704 bytes inside of
freed 1760-byte region [.ffff888065670760, ffff888065670e40)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x65670
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88802a080d01
flags: 0xfff80000000840(slab|head|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000840 ffff8880197f43c0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080110011 00000001ffffffff ffff88802a080d01
head: 00fff80000000840 ffff8880197f43c0 dead000000000122 0000000000000000
head: 0000000000000000 0000000080110011 00000001ffffffff ffff88802a080d01
head: 00fff80000000003 ffffea0001959c01 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5489, tgid -418021809 (syz-executor.0), ts 5490, free_ts 17403651762
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
__alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2175
allocate_slab mm/slub.c:2338 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2391
___slab_alloc+0xc73/0x1260 mm/slub.c:3525
__slab_alloc mm/slub.c:3610 [inline]
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
kmem_cache_alloc_lru+0x253/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_atomic_open+0x423/0x570 fs/ntfs3/namei.c:434
atomic_open fs/namei.c:3360 [inline]
lookup_open fs/namei.c:3468 [inline]
open_last_lookups fs/namei.c:3566 [inline]
path_openat+0x10bb/0x3350 fs/namei.c:3796
do_filp_open+0x235/0x490 fs/namei.c:3829
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
page last free pid 1 tgid 1 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
free_contig_range+0x9e/0x160 mm/page_alloc.c:6572
destroy_args+0x8a/0x890 mm/debug_vm_pgtable.c:1036
debug_vm_pgtable+0x4be/0x550 mm/debug_vm_pgtable.c:1416
do_one_initcall+0x248/0x880 init/main.c:1245
do_initcall_level+0x157/0x210 init/main.c:1307
do_initcalls+0x3f/0x80 init/main.c:1323
kernel_init_freeable+0x435/0x5d0 init/main.c:1555
kernel_init+0x1d/0x2b0 init/main.c:1444
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
ffff888065670d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888065670d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888065670e00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff888065670e80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
ffff888065670f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: e33c4963 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17912d17180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=144757d8980000

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

hdanton at sina

Apr 26, 2024, 11:29 PM

Post #5 of 10 (25 views)

Permalink

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 26, 2024, 11:52 PM

Post #6 of 10 (25 views)

Permalink

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in chrdev_open

loop0: detected capacity change from 0 to 4096
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
Read of size 8 at addr ffff88806dd4e688 by task syz-executor.0/5508

CPU: 0 PID: 5508 Comm: syz-executor.0 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add include/linux/list.h:169 [inline]
chrdev_open+0x2a9/0x630 fs/char_dev.c:396
do_dentry_open+0x90f/0x15b0 fs/open.c:956
do_open fs/namei.c:3642 [inline]
path_openat+0x2860/0x3240 fs/namei.c:3799
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1408
do_sys_open fs/open.c:1423 [inline]
__do_sys_openat fs/open.c:1439 [inline]
__se_sys_openat fs/open.c:1434 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1434
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8548c7dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f85499fd0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f8548dabf80 RCX: 00007f8548c7dea9
RDX: 0000000000000000 RSI: 0000000020002140 RDI: ffffffffffffff9c
RBP: 00007f8548cca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f8548dabf80 R15: 00007fff70180958
</TASK>

Allocated by task 5494:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_lru+0x178/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_mknod+0x41/0x60 fs/ntfs3/namei.c:128
vfs_mknod+0x36d/0x3b0 fs/namei.c:4001
do_mknodat+0x3ec/0x5b0
__do_sys_mknodat fs/namei.c:4079 [inline]
__se_sys_mknodat fs/namei.c:4076 [inline]
__x64_sys_mknodat+0xa9/0xc0 fs/namei.c:4076
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5504:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x10b/0x2c0 mm/slub.c:4344
rcu_do_batch kernel/rcu/tree.c:2196 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2471
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:2734 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:2838
__dentry_kill+0x20d/0x630 fs/dcache.c:603
shrink_kill+0xa9/0x2c0 fs/dcache.c:1048
shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1075
shrink_dcache_parent+0xcb/0x3b0
do_one_tree+0x23/0xe0 fs/dcache.c:1538
shrink_dcache_for_umount+0x7d/0x130 fs/dcache.c:1555
generic_shutdown_super+0x6a/0x2d0 fs/super.c:619
kill_block_super+0x44/0x90 fs/super.c:1675
ntfs3_kill_sb+0x44/0x1b0 fs/ntfs3/super.c:1785
deactivate_locked_super+0xc4/0x130 fs/super.c:472
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88806dd4dfe0
which belongs to the cache ntfs_inode_cache of size 1760
The buggy address is located 1704 bytes inside of
freed 1760-byte region [.ffff88806dd4dfe0, ffff88806dd4e6c0)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x6dd48
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888029458b01
flags: 0xfff80000000840(slab|head|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000840 ffff888019733b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080110011 00000001ffffffff ffff888029458b01
head: 00fff80000000840 ffff888019733b40 dead000000000122 0000000000000000
head: 0000000000000000 0000000080110011 00000001ffffffff ffff888029458b01
head: 00fff80000000003 ffffea0001b75201 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5493, tgid 401221234 (syz-executor.0), ts 5494, free_ts 64399791889
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
__alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2175
allocate_slab mm/slub.c:2338 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2391
___slab_alloc+0xc73/0x1260 mm/slub.c:3525
__slab_alloc mm/slub.c:3610 [inline]
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
kmem_cache_alloc_lru+0x253/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
iget5_locked+0xa4/0x280 fs/inode.c:1235
ntfs_iget5+0xc7/0x3b70 fs/ntfs3/inode.c:525
ntfs_fill_super+0x25dc/0x49c0 fs/ntfs3/super.c:1206
get_tree_bdev+0x3f7/0x570 fs/super.c:1614
vfs_get_tree+0x90/0x2a0 fs/super.c:1779
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
page last free pid 5059 tgid 5059 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
free_unref_folios+0x185/0xb30 mm/page_alloc.c:2536
folios_put_refs+0x8eb/0xa10 mm/swap.c:1034
free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:329
__tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
zap_pte_range mm/memory.c:1683 [inline]
zap_pmd_range mm/memory.c:1722 [inline]
zap_pud_range mm/memory.c:1751 [inline]
zap_p4d_range mm/memory.c:1772 [inline]
unmap_page_range+0x3e36/0x4820 mm/memory.c:1793
unmap_vmas+0x3cc/0x5f0 mm/memory.c:1883
exit_mmap+0x2cb/0xd60 mm/mmap.c:3267
__mmput+0x115/0x3c0 kernel/fork.c:1346
exit_mm+0x220/0x310 kernel/exit.c:569
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
get_signal+0x16a1/0x1740 kernel/signal.c:2911
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89

Memory state around the buggy address:
ffff88806dd4e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806dd4e600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88806dd4e680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff88806dd4e700: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
ffff88806dd4e780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: e33c4963 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=109b0028980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=12632380980000

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

hdanton at sina

Apr 27, 2024, 2:18 AM

Post #7 of 10 (25 views)

Permalink

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 27, 2024, 2:45 AM

Post #8 of 10 (25 views)

Permalink

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in chrdev_open

loop0: detected capacity change from 0 to 4096
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
Read of size 8 at addr ffff888054dc32e8 by task syz-executor.0/5507

CPU: 1 PID: 5507 Comm: syz-executor.0 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add include/linux/list.h:169 [inline]
chrdev_open+0x429/0x680 fs/char_dev.c:398
do_dentry_open+0x907/0x15a0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x2860/0x3240 fs/namei.c:3799
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8a3ae7dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8a3bb910c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f8a3afabf80 RCX: 00007f8a3ae7dea9
RDX: 0000000000000000 RSI: 0000000020002140 RDI: ffffffffffffff9c
RBP: 00007f8a3aeca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f8a3afabf80 R15: 00007ffd8c82a438
</TASK>

Allocated by task 5494:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_lru+0x178/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_mknod+0x41/0x60 fs/ntfs3/namei.c:128
vfs_mknod+0x36d/0x3b0 fs/namei.c:4001
do_mknodat+0x3ec/0x5b0
__do_sys_mknodat fs/namei.c:4079 [inline]
__se_sys_mknodat fs/namei.c:4076 [inline]
__x64_sys_mknodat+0xa9/0xc0 fs/namei.c:4076
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 782:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x10b/0x2c0 mm/slub.c:4344
rcu_do_batch kernel/rcu/tree.c:2196 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2471
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:2734 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:2838
__dentry_kill+0x20d/0x630 fs/dcache.c:603
shrink_kill+0xa9/0x2c0 fs/dcache.c:1048
shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1075
shrink_dcache_parent+0xcb/0x3b0
do_one_tree+0x23/0xe0 fs/dcache.c:1538
shrink_dcache_for_umount+0x7d/0x130 fs/dcache.c:1555
generic_shutdown_super+0x6a/0x2d0 fs/super.c:619
kill_block_super+0x44/0x90 fs/super.c:1675
ntfs3_kill_sb+0x44/0x1b0 fs/ntfs3/super.c:1785
deactivate_locked_super+0xc4/0x130 fs/super.c:472
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888054dc2c40
which belongs to the cache ntfs_inode_cache of size 1760
The buggy address is located 1704 bytes inside of
freed 1760-byte region [.ffff888054dc2c40, ffff888054dc3320)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x54dc0
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888029883001
flags: 0xfff80000000840(slab|head|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000840 ffff8880193ed000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000110011 00000001ffffffff ffff888029883001
head: 00fff80000000840 ffff8880193ed000 dead000000000122 0000000000000000
head: 0000000000000000 0000000000110011 00000001ffffffff ffff888029883001
head: 00fff80000000003 ffffea0001537001 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5493, tgid -24364326 (syz-executor.0), ts 5494, free_ts 85127425274
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
__alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2175
allocate_slab mm/slub.c:2338 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2391
___slab_alloc+0xc73/0x1260 mm/slub.c:3525
__slab_alloc mm/slub.c:3610 [inline]
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
kmem_cache_alloc_lru+0x253/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
iget5_locked+0xa4/0x280 fs/inode.c:1235
ntfs_iget5+0xc7/0x3b70 fs/ntfs3/inode.c:525
ntfs_extend_init+0x11f/0x530 fs/ntfs3/fsntfs.c:224
ntfs_fill_super+0x430a/0x49c0 fs/ntfs3/super.c:1531
get_tree_bdev+0x3f7/0x570 fs/super.c:1614
vfs_get_tree+0x90/0x2a0 fs/super.c:1779
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
page last free pid 4525 tgid 4525 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
free_unref_page+0x37/0x3f0 mm/page_alloc.c:2487
discard_slab mm/slub.c:2437 [inline]
__put_partials+0xeb/0x130 mm/slub.c:2906
put_cpu_partial+0x17c/0x250 mm/slub.c:2981
__slab_free+0x2ea/0x3d0 mm/slub.c:4151
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x5e/0xc0 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:322
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc+0x174/0x340 mm/slub.c:3852
getname_flags+0xbd/0x4f0 fs/namei.c:139
vfs_fstatat+0x11c/0x190 fs/stat.c:303
__do_sys_newfstatat fs/stat.c:468 [inline]
__se_sys_newfstatat fs/stat.c:462 [inline]
__x64_sys_newfstatat+0x117/0x190 fs/stat.c:462
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888054dc3180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888054dc3200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888054dc3280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888054dc3300: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
ffff888054dc3380: fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: e33c4963 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=15eed908980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=139f8f0f180000

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

hdanton at sina

Apr 27, 2024, 3:44 AM

Post #9 of 10 (25 views)

Permalink

On Fri, 26 Apr 2024 05:00:21 -0700
> syzbot found the following issue on:
>
> HEAD commit: e33c4963bf53 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
> git tree: upstream
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12499380980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git e33c4963bf53

--- x/fs/char_dev.c
+++ y/fs/char_dev.c
@@ -377,6 +377,9 @@ static int chrdev_open(struct inode *ino
struct cdev *new = NULL;
int ret = 0;

+ if (!igrab(inode))
+ return -ENXIO;
+
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
@@ -384,8 +387,10 @@ static int chrdev_open(struct inode *ino
int idx;
spin_unlock(&cdev_lock);
kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
- if (!kobj)
+ if (!kobj) {
+ iput(inode);
return -ENXIO;
+ }
new = container_of(kobj, struct cdev, kobj);
spin_lock(&cdev_lock);
/* Check i_cdev again in case somebody beat us to it while
@@ -401,8 +406,10 @@ static int chrdev_open(struct inode *ino
ret = -ENXIO;
spin_unlock(&cdev_lock);
cdev_put(new);
- if (ret)
+ if (ret) {
+ iput(inode);
return ret;
+ }

ret = -ENXIO;
fops = fops_get(p->ops);
@@ -416,10 +423,12 @@ static int chrdev_open(struct inode *ino
goto out_cdev_put;
}

+ iput(inode);
return 0;

out_cdev_put:
cdev_put(p);
+ iput(inode);
return ret;
}

--

Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open [ In reply to ]

syzbot+5d34cc6474499a5ff516 at syzkaller

Apr 27, 2024, 3:58 AM

Post #10 of 10 (25 views)

Permalink

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in chrdev_open

loop0: detected capacity change from 0 to 4096
==================================================================
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
Read of size 8 at addr ffff8880699bc908 by task syz-executor.0/5501

CPU: 1 PID: 5501 Comm: syz-executor.0 Not tainted 6.9.0-rc5-syzkaller-00053-ge33c4963bf53-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
__list_add_valid_or_report+0x4c/0xf0 lib/list_debug.c:29
__list_add_valid include/linux/list.h:88 [inline]
__list_add include/linux/list.h:150 [inline]
list_add include/linux/list.h:169 [inline]
chrdev_open+0x2de/0x680 fs/char_dev.c:401
do_dentry_open+0x907/0x15a0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x2860/0x3240 fs/namei.c:3799
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7dd5a7dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7dd67280c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f7dd5babf80 RCX: 00007f7dd5a7dea9
RDX: 0000000000000000 RSI: 0000000020002140 RDI: ffffffffffffff9c
RBP: 00007f7dd5aca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f7dd5babf80 R15: 00007ffd9078e268
</TASK>

Allocated by task 5488:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3798 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_lru+0x178/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
new_inode_pseudo+0x69/0x1e0 fs/inode.c:1007
new_inode+0x22/0x1d0 fs/inode.c:1033
ntfs_new_inode+0x45/0x100 fs/ntfs3/fsntfs.c:1688
ntfs_create_inode+0x687/0x3c30 fs/ntfs3/inode.c:1333
ntfs_mknod+0x41/0x60 fs/ntfs3/namei.c:128
vfs_mknod+0x36d/0x3b0 fs/namei.c:4001
do_mknodat+0x3ec/0x5b0
__do_sys_mknodat fs/namei.c:4079 [inline]
__se_sys_mknodat fs/namei.c:4076 [inline]
__x64_sys_mknodat+0xa9/0xc0 fs/namei.c:4076
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5496:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kmem_cache_free+0x10b/0x2c0 mm/slub.c:4344
rcu_do_batch kernel/rcu/tree.c:2196 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2471
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:2734 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:2838
__dentry_kill+0x20d/0x630 fs/dcache.c:603
shrink_kill+0xa9/0x2c0 fs/dcache.c:1048
shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1075
shrink_dcache_parent+0xcb/0x3b0
do_one_tree+0x23/0xe0 fs/dcache.c:1538
shrink_dcache_for_umount+0x7d/0x130 fs/dcache.c:1555
generic_shutdown_super+0x6a/0x2d0 fs/super.c:619
kill_block_super+0x44/0x90 fs/super.c:1675
ntfs3_kill_sb+0x44/0x1b0 fs/ntfs3/super.c:1785
deactivate_locked_super+0xc4/0x130 fs/super.c:472
cleanup_mnt+0x426/0x4c0 fs/namespace.c:1267
task_work_run+0x24f/0x310 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880699bc260
which belongs to the cache ntfs_inode_cache of size 1760
The buggy address is located 1704 bytes inside of
freed 1760-byte region [.ffff8880699bc260, ffff8880699bc940)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x699b8
head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88802aa7de01
flags: 0xfff80000000840(slab|head|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000840 ffff888017be5c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000110011 00000001ffffffff ffff88802aa7de01
head: 00fff80000000840 ffff888017be5c80 dead000000000122 0000000000000000
head: 0000000000000000 0000000000110011 00000001ffffffff ffff88802aa7de01
head: 00fff80000000003 ffffea0001a66e01 dead000000000122 00000000ffffffff
head: 0000000800000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5487, tgid -241896813 (syz-executor.0), ts 5488, free_ts 64557978708
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
__alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2175
allocate_slab mm/slub.c:2338 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2391
___slab_alloc+0xc73/0x1260 mm/slub.c:3525
__slab_alloc mm/slub.c:3610 [inline]
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
kmem_cache_alloc_lru+0x253/0x350 mm/slub.c:3864
alloc_inode_sb include/linux/fs.h:3091 [inline]
ntfs_alloc_inode+0x28/0x80 fs/ntfs3/super.c:557
alloc_inode fs/inode.c:261 [inline]
iget5_locked+0xa4/0x280 fs/inode.c:1235
ntfs_iget5+0xc7/0x3b70 fs/ntfs3/inode.c:525
ntfs_fill_super+0x34f4/0x49c0 fs/ntfs3/super.c:1368
get_tree_bdev+0x3f7/0x570 fs/super.c:1614
vfs_get_tree+0x90/0x2a0 fs/super.c:1779
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
page last free pid 5066 tgid 5060 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
free_unref_folios+0x185/0xb30 mm/page_alloc.c:2536
folios_put_refs+0x8eb/0xa10 mm/swap.c:1034
free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:329
__tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
zap_pte_range mm/memory.c:1683 [inline]
zap_pmd_range mm/memory.c:1722 [inline]
zap_pud_range mm/memory.c:1751 [inline]
zap_p4d_range mm/memory.c:1772 [inline]
unmap_page_range+0x3e36/0x4820 mm/memory.c:1793
unmap_vmas+0x3cc/0x5f0 mm/memory.c:1883
exit_mmap+0x2cb/0xd60 mm/mmap.c:3267
__mmput+0x115/0x3c0 kernel/fork.c:1346
exit_mm+0x220/0x310 kernel/exit.c:569
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
get_signal+0x16a1/0x1740 kernel/signal.c:2911
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89

Memory state around the buggy address:
ffff8880699bc800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880699bc880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880699bc900: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
^
ffff8880699bc980: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
ffff8880699bca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: e33c4963 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1507f237180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=5d34cc6474499a5ff516
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=137728a7180000