[v5.15] KASAN: use-after-free Write in nfsd_shutdown_threads
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syzbot
Jul 27, 2026, 4:38:27 AM (12 days ago) Jul 27
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1474c49e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=ae02940eff06b915b7ab
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae0294...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
Write of size 4 at addr ffff8880252af450 by task syz-executor/4186
CPU: 0 PID: 4186 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
__refcount_add include/linux/refcount.h:193 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
nfsd_umount+0x3e/0xc0 fs/nfsd/nfsctl.c:1411
deactivate_locked_super+0x93/0xf0 fs/super.c:335
cleanup_mnt+0x426/0x4d0 fs/namespace.c:1148
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8213c010d7
Code: a2 c7 05 1c 26 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffffcf61108 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f8213c010d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffffcf611c0
RBP: 00007ffffcf611c0 R08: 00007ffffcf621c0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffffcf62250
R13: 00007f8213c9530a R14: 000000000001112d R15: 00007ffffcf62290
</TASK>
Allocated by task 4276:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
__svc_create+0x60/0x9d0 net/sunrpc/svc.c:458
svc_create_pooled+0x62f/0x810 net/sunrpc/svc.c:546
nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:668
nfsd_svc+0x132/0x9e0 fs/nfsd/nfssvc.c:798
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 4276:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
kref_put include/linux/kref.h:65 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
nfsd_svc+0x7cf/0x9e0 fs/nfsd/nfssvc.c:821
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
The buggy address belongs to the object at ffff8880252af400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
512-byte region [ffff8880252af400, ffff8880252af600)
The buggy address belongs to the page:
page:ffffea000094ab00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x252ac
head:ffffea000094ab00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888016c41c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 3558, ts 69515701897, free_ts 66491796932
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x807/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
netlink_sendmsg+0x654/0xbe0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
__sys_sendmsg net/socket.c:2529 [inline]
__do_sys_sendmsg net/socket.c:2538 [inline]
__se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmem_cache_alloc_trace+0x165/0x290 mm/slub.c:3250
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
tomoyo_dump_page+0xe7/0x5f0 security/tomoyo/domain.c:909
tomoyo_scan_bprm security/tomoyo/condition.c:130 [inline]
tomoyo_condition+0x206f/0x2d90 security/tomoyo/condition.c:1120
tomoyo_check_acl+0x192/0x420 security/tomoyo/domain.c:177
tomoyo_execute_permission+0x11f/0x400 security/tomoyo/file.c:615
tomoyo_find_next_domain+0x442/0x1a50 security/tomoyo/domain.c:755
tomoyo_bprm_check_security+0xdd/0x120 security/tomoyo/tomoyo.c:101
security_bprm_check+0x5e/0x90 security/security.c:869
Memory state around the buggy address:
ffff8880252af300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880252af380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880252af400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880252af480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880252af500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
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https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
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If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1474c49e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=ae02940eff06b915b7ab
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae0294...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
Write of size 4 at addr ffff8880252af450 by task syz-executor/4186
CPU: 0 PID: 4186 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x235/0x290 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
__refcount_add include/linux/refcount.h:193 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
nfsd_umount+0x3e/0xc0 fs/nfsd/nfsctl.c:1411
deactivate_locked_super+0x93/0xf0 fs/super.c:335
cleanup_mnt+0x426/0x4d0 fs/namespace.c:1148
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8213c010d7
Code: a2 c7 05 1c 26 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffffcf61108 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f8213c010d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffffcf611c0
RBP: 00007ffffcf611c0 R08: 00007ffffcf621c0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffffcf62250
R13: 00007f8213c9530a R14: 000000000001112d R15: 00007ffffcf62290
</TASK>
Allocated by task 4276:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
__svc_create+0x60/0x9d0 net/sunrpc/svc.c:458
svc_create_pooled+0x62f/0x810 net/sunrpc/svc.c:546
nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:668
nfsd_svc+0x132/0x9e0 fs/nfsd/nfssvc.c:798
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 4276:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
kref_put include/linux/kref.h:65 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
nfsd_svc+0x7cf/0x9e0 fs/nfsd/nfssvc.c:821
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
The buggy address belongs to the object at ffff8880252af400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
512-byte region [ffff8880252af400, ffff8880252af600)
The buggy address belongs to the page:
page:ffffea000094ab00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x252ac
head:ffffea000094ab00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888016c41c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 3558, ts 69515701897, free_ts 66491796932
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x807/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
netlink_sendmsg+0x654/0xbe0 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2446
___sys_sendmsg+0x236/0x2e0 net/socket.c:2500
__sys_sendmsg net/socket.c:2529 [inline]
__do_sys_sendmsg net/socket.c:2538 [inline]
__se_sys_sendmsg+0x1b7/0x2a0 net/socket.c:2536
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmem_cache_alloc_trace+0x165/0x290 mm/slub.c:3250
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
tomoyo_dump_page+0xe7/0x5f0 security/tomoyo/domain.c:909
tomoyo_scan_bprm security/tomoyo/condition.c:130 [inline]
tomoyo_condition+0x206f/0x2d90 security/tomoyo/condition.c:1120
tomoyo_check_acl+0x192/0x420 security/tomoyo/domain.c:177
tomoyo_execute_permission+0x11f/0x400 security/tomoyo/file.c:615
tomoyo_find_next_domain+0x442/0x1a50 security/tomoyo/domain.c:755
tomoyo_bprm_check_security+0xdd/0x120 security/tomoyo/tomoyo.c:101
security_bprm_check+0x5e/0x90 security/security.c:869
Memory state around the buggy address:
ffff8880252af300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880252af380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880252af400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880252af480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880252af500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot
Jul 27, 2026, 4:48:31 AM (12 days ago) Jul 27
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: dc5c83b7f5f8 Linux 6.1.178
syzbot found the following issue on:
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=120cc49e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=7e7efd143acb9c5131e3
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
vmlinux: https://storage.googleapis.com/syzbot-assets/0d4afce44fab/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4787e310d875/Image-dc5c83b7.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_shutdown_threads+0x90/0x204 fs/nfsd/nfssvc.c:640
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
Write of size 4 at addr ffff0000f3977450 by task syz-executor/4328
CPU: 0 PID: 4328 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
print_address_description+0x88/0x218 mm/kasan/report.c:316
print_report+0x50/0x68 mm/kasan/report.c:420
kasan_report+0xa8/0xfc mm/kasan/report.c:524
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x258/0x290 mm/kasan/generic.c:189
__kasan_check_write+0x2c/0x3c mm/kasan/shadow.c:37
instrument_atomic_read_write include/linux/instrumented.h:102 [inline]
atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [inline]
__refcount_add include/linux/refcount.h:193 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_shutdown_threads+0x90/0x204 fs/nfsd/nfssvc.c:640
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409
deactivate_locked_super+0xb4/0x128 fs/super.c:332
deactivate_super+0xe4/0x104 fs/super.c:363
cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191
__cleanup_mnt+0x20/0x30 fs/namespace.c:1198
task_work_run+0x1f4/0x280 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Allocated by task 4603:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
____kasan_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
kmalloc_trace+0x7c/0x94 mm/slab_common.c:1031
kmalloc include/linux/slab.h:563 [inline]
kzalloc include/linux/slab.h:699 [inline]
__svc_create+0x80/0x89c net/sunrpc/svc.c:464
svc_create_pooled+0x648/0x7d8 net/sunrpc/svc.c:552
nfsd_create_serv+0x284/0x6a4 fs/nfsd/nfssvc.c:667
__write_ports_addfd fs/nfsd/nfsctl.c:716 [inline]
__write_ports fs/nfsd/nfsctl.c:791 [inline]
write_ports+0x3b8/0x9f0 fs/nfsd/nfsctl.c:847
nfsctl_transaction_write+0x114/0x164 fs/nfsd/nfsctl.c:114
vfs_write+0x2a8/0x7c8 fs/read_write.c:582
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Freed by task 4603:
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
__kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xbc/0x21c mm/slub.c:3700
kfree+0xd0/0x1a8 mm/slab_common.c:988
svc_destroy+0x144/0x184 net/sunrpc/svc.c:586
kref_put include/linux/kref.h:65 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
__write_ports_addfd fs/nfsd/nfsctl.c:728 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
__write_ports fs/nfsd/nfsctl.c:791 [inline]
write_ports+0x7dc/0x9f0 fs/nfsd/nfsctl.c:847
nfsctl_transaction_write+0x114/0x164 fs/nfsd/nfsctl.c:114
vfs_write+0x2a8/0x7c8 fs/read_write.c:582
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
The buggy address belongs to the object at ffff0000f3977400
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
512-byte region [ffff0000f3977400, ffff0000f3977600)
The buggy address is located 80 bytes inside of
The buggy address belongs to the physical page:
page:0000000077ee52d3 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x133974
head:0000000077ee52d3 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 0000000000000000 dead000000000001 ffff0000c0002600
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff0000f3977300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff0000f3977380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000f3977400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff0000f3977480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff0000f3977500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 4328 at lib/refcount.c:25 refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25
Modules linked in:
CPU: 0 PID: 4328 Comm: syz-executor Tainted: G B syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25
lr : refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25
sp : ffff800020a779b0
x29: ffff800020a779b0 x28: ffff0000dd14a900 x27: ffff0000dd14a900
x26: dfff800000000000 x25: 0000000000000002 x24: 0000000000000002
x23: 0000000000000003 x22: 0000000000000000 x21: ffff0000f3977400
x20: ffff0000f3977450 x19: ffff800017d5d000 x18: 1fffe00033e7277e
x17: ffff80001537d000 x16: ffff800008043b30 x15: ffff00019f393bfc
x14: 0000000000000001 x13: 1fffe0001ad7fa90 x12: 0000000000000000
x11: 0000000000000000 x10: ffff60001ad7fa91 x9 : 959fa834eed28c00
x8 : 959fa834eed28c00 x7 : ffff800011cec160 x6 : ffff80000825ab4c
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff800008249818
x2 : 0000000000000001 x1 : 0000000000000004 x0 : 0000000000000001
Call trace:
refcount_warn_saturate+0x134/0x1f8 lib/refcount.c:25
__refcount_add include/linux/refcount.h:-1 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_shutdown_threads+0x188/0x204 fs/nfsd/nfssvc.c:640
refcount_inc include/linux/refcount.h:267 [inline]
kref_get include/linux/kref.h:45 [inline]
svc_get include/linux/sunrpc/svc.h:108 [inline]
nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409
deactivate_locked_super+0xb4/0x128 fs/super.c:332
deactivate_super+0xe4/0x104 fs/super.c:363
cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191
__cleanup_mnt+0x20/0x30 fs/namespace.c:1198
task_work_run+0x1f4/0x280 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 230709
hardirqs last enabled at (230709): [<ffff80000825abe0>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline]
hardirqs last enabled at (230709): [<ffff80000825abe0>] finish_lock_switch+0xb0/0x1c8 kernel/sched/core.c:5005
hardirqs last disabled at (230708): [<ffff800011c635b8>] __schedule+0x294/0x1a6c kernel/sched/core.c:6461
softirqs last enabled at (230556): [<ffff800008031254>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (230554): [<ffff800008031220>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---
Unable to handle kernel paging request at virtual address dfff800000000006
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000006] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4328 Comm: syz-executor Tainted: G B W syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 02400005 (nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : svc_unregister+0x130/0x624 net/sunrpc/svc.c:1143
lr : svc_unregister+0x120/0x624 net/sunrpc/svc.c:1141
sp : ffff800020a778d0
x29: ffff800020a77900 x28: dfff800000000000 x27: ffff0000cb263e18
x26: ffff0000d6a68000 x25: 0000000000000030 x24: 000000000000001c
x23: ffff0000cb263e14 x22: 1fffe0001964c7c2 x21: ffff0000cb263e00
x20: 1fffe0001964c7c3 x19: 00000000000000e0 x18: 1fffe00033e7277e
x17: ffff80001537d000 x16: ffff800011b90540 x15: 0000000000000000
x14: 0000000011b8cc18 x13: 0000000054c68a56 x12: ffff800008021d48
x11: ff00800010f0acf4 x10: 0000000000000000 x9 : ffff80001c5fab10
x8 : 0000000000000006 x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 0000000000000001 x3 : ffff800010f0ab54
x2 : 0000000000000000 x1 : 0000000000000008 x0 : 0000000000000000
Call trace:
svc_unregister+0x130/0x624 net/sunrpc/svc.c:1143
svc_rpcb_cleanup+0x28/0x40 net/sunrpc/svc.c:407
nfsd_last_thread+0x114/0x2e4 fs/nfsd/nfssvc.c:560
nfsd_shutdown_threads+0xe4/0x204 fs/nfsd/nfssvc.c:643
nfsd_umount+0x48/0xf8 fs/nfsd/nfsctl.c:1409
deactivate_locked_super+0xb4/0x128 fs/super.c:332
deactivate_super+0xe4/0x104 fs/super.c:363
cleanup_mnt+0x3a8/0x430 fs/namespace.c:1191
__cleanup_mnt+0x20/0x30 fs/namespace.c:1198
task_work_run+0x1f4/0x280 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
do_notify_resume+0x20f8/0x2c84 arch/arm64/kernel/signal.c:1151
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: f8736b28 b4000148 91007119 d343ff28 (38fc6908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: f8736b28 ldr x8, [x25, x19]
4: b4000148 cbz x8, 0x2c
8: 91007119 add x25, x8, #0x1c
c: d343ff28 lsr x8, x25, #3
* 10: 38fc6908 ldrsb w8, [x8, x28] <-- trapping instruction
syzbot
Jul 29, 2026, 7:13:25 AM (10 days ago) Jul 29
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:
HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17b98aea580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13e06249580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae0294...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
Write of size 4 at addr ffff888023ca2850 by task syz-executor/4285
CPU: 0 PID: 4285 Comm: syz-executor Not tainted syzkaller #0
RIP: 0033:0x7f86fb3b70d7
RAX: 0000000000000000 RBX: 00007f86fb44b30a RCX: 00007f86fb3b70d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe9ee5c7e0
RBP: 00007ffe9ee5c7e0 R08: 00007ffe9ee5d7e0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe9ee5d870
R13: 00007f86fb44b30a R14: 0000000000012f00 R15: 00007ffe9ee5d8b0
</TASK>
Allocated by task 4348:
head:ffffea00008f2800 order:2 compound_mapcount:0 compound_pincount:0
uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
kobject_uevent_net_broadcast+0x2e6/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x550/0x890 lib/kobject_uevent.c:608
kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
store_uevent+0x12/0x20 kernel/module.c:1167
module_attr_store+0x5b/0x80 kernel/params.c:905
kernfs_fop_write_iter+0x3a8/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x748/0xd70 fs/read_write.c:594
kmalloc include/linux/slab.h:612 [inline]
kernfs_fop_write_iter+0x14f/0x500 fs/kernfs/file.c:273
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x748/0xd70 fs/read_write.c:594
ffff888023ca2780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888023ca2800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888023ca2880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888023ca2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=ae02940eff06b915b7ab
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10d959b9580000
dashboard link: https://syzkaller.appspot.com/bug?extid=ae02940eff06b915b7ab
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13e06249580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae0294...@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: use-after-free in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: use-after-free in kref_get include/linux/kref.h:45 [inline]
BUG: KASAN: use-after-free in svc_get include/linux/sunrpc/svc.h:108 [inline]
BUG: KASAN: use-after-free in nfsd_shutdown_threads+0x89/0x1a0 fs/nfsd/nfssvc.c:641
CPU: 0 PID: 4285 Comm: syz-executor Not tainted syzkaller #0
Code: a2 c7 05 1c 26 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffe9ee5c728 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f86fb44b30a RCX: 00007f86fb3b70d7
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe9ee5c7e0
RBP: 00007ffe9ee5c7e0 R08: 00007ffe9ee5d7e0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe9ee5d870
R13: 00007f86fb44b30a R14: 0000000000012f00 R15: 00007ffe9ee5d8b0
</TASK>
Allocated by task 4348:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
__svc_create+0x60/0x9d0 net/sunrpc/svc.c:458
svc_create_pooled+0x62f/0x810 net/sunrpc/svc.c:546
nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:668
nfsd_svc+0x132/0x9e0 fs/nfsd/nfssvc.c:798
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Freed by task 4348:
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
____kasan_kmalloc mm/kasan/common.c:513 [inline]
__kasan_kmalloc+0xaf/0xe0 mm/kasan/common.c:522
kmalloc include/linux/slab.h:607 [inline]
kzalloc include/linux/slab.h:738 [inline]
__svc_create+0x60/0x9d0 net/sunrpc/svc.c:458
svc_create_pooled+0x62f/0x810 net/sunrpc/svc.c:546
nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:668
nfsd_svc+0x132/0x9e0 fs/nfsd/nfssvc.c:798
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
kref_put include/linux/kref.h:65 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
nfsd_svc+0x7cf/0x9e0 fs/nfsd/nfssvc.c:821
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
The buggy address belongs to the object at ffff888023ca2800
kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
kasan_slab_free include/linux/kasan.h:230 [inline]
slab_free_hook mm/slub.c:1710 [inline]
slab_free_freelist_hook+0xec/0x170 mm/slub.c:1736
slab_free mm/slub.c:3504 [inline]
kfree+0xef/0x2a0 mm/slub.c:4564
kref_put include/linux/kref.h:65 [inline]
svc_put include/linux/sunrpc/svc.h:123 [inline]
nfsd_svc+0x7cf/0x9e0 fs/nfsd/nfssvc.c:821
write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:426
nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
vfs_write+0x304/0xd70 fs/read_write.c:592
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
512-byte region [ffff888023ca2800, ffff888023ca2a00)
The buggy address is located 80 bytes inside of
The buggy address belongs to the page:
page:ffffea00008f2800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x23ca0
head:ffffea00008f2800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888016c41c80
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3560, ts 26473931334, free_ts 26439216648
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
prep_new_page mm/page_alloc.c:2426 [inline]
get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x807/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:290
get_page_from_freelist+0x24f6/0x2670 mm/page_alloc.c:4192
__alloc_pages+0x1ee/0x480 mm/page_alloc.c:5501
alloc_slab_page mm/slub.c:1780 [inline]
allocate_slab mm/slub.c:1917 [inline]
new_slab+0xc0/0x4b0 mm/slub.c:1980
___slab_alloc+0x807/0xdd0 mm/slub.c:3013
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
kobject_uevent_net_broadcast+0x2e6/0x530 lib/kobject_uevent.c:409
kobject_uevent_env+0x550/0x890 lib/kobject_uevent.c:608
kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
store_uevent+0x12/0x20 kernel/module.c:1167
module_attr_store+0x5b/0x80 kernel/params.c:905
kernfs_fop_write_iter+0x3a8/0x500 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x748/0xd70 fs/read_write.c:594
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
__kmalloc+0x189/0x340 mm/slub.c:4408
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1340 [inline]
free_pcp_prepare mm/page_alloc.c:1391 [inline]
free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
free_unref_page+0x8f/0x2a0 mm/page_alloc.c:3396
free_slab mm/slub.c:2020 [inline]
discard_slab mm/slub.c:2026 [inline]
__unfreeze_partials+0x188/0x1e0 mm/slub.c:2512
put_cpu_partial+0x12d/0x190 mm/slub.c:2592
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xc0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3225 [inline]
slab_alloc mm/slub.c:3233 [inline]
kmalloc include/linux/slab.h:612 [inline]
kernfs_fop_write_iter+0x14f/0x500 fs/kernfs/file.c:273
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x748/0xd70 fs/read_write.c:594
ksys_write+0x153/0x260 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
Memory state around the buggy address:
ffff888023ca2700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888023ca2780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888023ca2800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888023ca2880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888023ca2900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
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