KASAN: use-after-free Write in nfsd_shutdown_threads

Status: upstream: reported on 2026/07/27 08:48
Reported-by: syzbot+7e7efd143acb9c5131e3@syzkaller.appspotmail.com
First crash: 109d, last: 1d14h
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Write in nfsd_shutdown_threads origin:lts-only 22 syz, C 2175 49m 109d 0/3 upstream: reported C repro on 2026/07/27 08:38
linux-6.6 KASAN: slab-use-after-free Write in nfsd_shutdown_threads 22 syz 48 1d02h 108d 0/2 upstream: reported syz repro on 2026/07/27 20:29

Sample crash report:
==================================================================
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+0x89/0x1a0 fs/nfsd/nfssvc.c:640
Write of size 4 at addr ffff88805763ec50 by task syz-executor/4275

CPU: 0 PID: 4275 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 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: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+0x89/0x1a0 fs/nfsd/nfssvc.c:640
 nfsd_umount+0x3e/0xc0 fs/nfsd/nfsctl.c:1409
 deactivate_locked_super+0x93/0xf0 fs/super.c:332
 cleanup_mnt+0x471/0x4f0 fs/namespace.c:1191
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:180
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:295 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:306
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa1d6da0d57
Code: a2 c7 05 9c a9 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:00007ffe2f995038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fa1d6e36fb3 RCX: 00007fa1d6da0d57
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe2f9950f0
RBP: 00007ffe2f9950f0 R08: 00007ffe2f9960f0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe2f996180
R13: 00007fa1d6e36fb3 R14: 000000000005bde9 R15: 00007ffe2f9961c0
 </TASK>

Allocated by task 7087:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 __svc_create+0x60/0x9d0 net/sunrpc/svc.c:491
 svc_create_pooled+0x71f/0x8c0 net/sunrpc/svc.c:579
 nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:667
 __write_ports_addfd fs/nfsd/nfsctl.c:716 [inline]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0x526/0xb80 fs/nfsd/nfsctl.c:847
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 7087:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1735 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1761
 slab_free mm/slub.c:3694 [inline]
 __kmem_cache_free+0xb6/0x200 mm/slub.c:3707
 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]
 __write_ports fs/nfsd/nfsctl.c:791 [inline]
 write_ports+0x9ac/0xb80 fs/nfsd/nfsctl.c:847
 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114
 vfs_write+0x2dc/0x9a0 fs/read_write.c:582
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805763ec00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
 512-byte region [ffff88805763ec00, ffff88805763ee00)

The buggy address belongs to the physical page:
page:ffffea00015d8f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5763c
head:ffffea00015d8f00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888018441c80
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 4279, tgid 4279 (syz-executor), ts 67701493308, free_ts 21677023236
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
 prep_new_page mm/page_alloc.c:2567 [inline]
 get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
 alloc_slab_page+0x5d/0x180 mm/slub.c:1805
 allocate_slab mm/slub.c:1950 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2003
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3161
 __slab_alloc mm/slub.c:3247 [inline]
 slab_alloc_node mm/slub.c:3332 [inline]
 __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3405
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc_node_track_caller+0xa0/0x240 mm/slab_common.c:956
 kmalloc_reserve net/core/skbuff.c:446 [inline]
 __alloc_skb+0x226/0x7d0 net/core/skbuff.c:515
 alloc_skb include/linux/skbuff.h:1303 [inline]
 alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:290
 uevent_net_broadcast_tagged lib/kobject_uevent.c:351 [inline]
 kobject_uevent_net_broadcast+0x17e/0x530 lib/kobject_uevent.c:412
 kobject_uevent_env+0x555/0x890 lib/kobject_uevent.c:608
 rx_queue_add_kobject net/core/net-sysfs.c:1072 [inline]
 net_rx_queue_update_kobjects+0x244/0x4d0 net/core/net-sysfs.c:1112
 register_queue_kobjects net/core/net-sysfs.c:1772 [inline]
 netdev_register_kobject+0x231/0x320 net/core/net-sysfs.c:2017
 register_netdevice+0x133a/0x1b80 net/core/dev.c:10266
 ipvlan_link_new+0x389/0xae0 drivers/net/ipvlan/ipvlan_main.c:590
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 free_contig_range+0x9d/0x150 mm/page_alloc.c:9506
 destroy_args+0xef/0xa0e mm/debug_vm_pgtable.c:1031
 debug_vm_pgtable+0x33c/0x38e mm/debug_vm_pgtable.c:1359
 do_one_initcall+0x257/0x800 init/main.c:1271
 do_initcall_level+0x13d/0x1ed init/main.c:1344
 do_initcalls+0x4b/0x8a init/main.c:1360
 kernel_init_freeable+0x401/0x5ab init/main.c:1599
 kernel_init+0x19/0x1b0 init/main.c:1487
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff88805763eb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805763eb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805763ec00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88805763ec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805763ed00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (83):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/04 00:13 linux-6.1.y 08889840163e e2d35131 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/03 22:32 linux-6.1.y 08889840163e e2d35131 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/31 04:36 linux-6.1.y 08889840163e 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/22 23:02 linux-6.1.y 79807e970724 b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/06 05:16 linux-6.1.y a500ba24937a f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/05 04:19 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/05 00:13 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/22 11:12 linux-6.1.y 1a8763b93150 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/17 23:15 linux-6.1.y 1a8763b93150 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/17 23:13 linux-6.1.y 1a8763b93150 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/15 00:09 linux-6.1.y 1a8763b93150 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/18 06:45 linux-6.1.y e4f7d8be268e 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/17 20:44 linux-6.1.y e4f7d8be268e 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/17 18:57 linux-6.1.y e4f7d8be268e 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/17 17:49 linux-6.1.y e4f7d8be268e 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/14 08:16 linux-6.1.y e4f7d8be268e b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/14 07:43 linux-6.1.y e4f7d8be268e b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/12 10:58 linux-6.1.y e4f7d8be268e f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/28 00:09 linux-6.1.y dc5c83b7f5f8 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/28 00:09 linux-6.1.y dc5c83b7f5f8 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/28 00:07 linux-6.1.y dc5c83b7f5f8 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/27 23:39 linux-6.1.y dc5c83b7f5f8 aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/11 23:24 linux-6.1.y c75b0cf0982c e56a968c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/11 21:32 linux-6.1.y c75b0cf0982c e56a968c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/05 04:27 linux-6.1.y 08889840163e 73438ed0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/03 02:26 linux-6.1.y 08889840163e 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/02 18:44 linux-6.1.y 08889840163e 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/11/01 00:43 linux-6.1.y 08889840163e 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/28 09:34 linux-6.1.y 79807e970724 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/28 08:04 linux-6.1.y 79807e970724 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/21 13:15 linux-6.1.y 79807e970724 61c200c7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/16 22:29 linux-6.1.y 79807e970724 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/16 18:55 linux-6.1.y 79807e970724 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/16 18:43 linux-6.1.y 79807e970724 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/13 16:42 linux-6.1.y a500ba24937a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/13 15:22 linux-6.1.y a500ba24937a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/04 17:57 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/10/04 15:49 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/28 19:07 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/23 02:31 linux-6.1.y 1a8763b93150 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/22 13:03 linux-6.1.y 1a8763b93150 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/09/19 18:49 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/31 21:04 linux-6.1.y d64a499eea6b 316d9396 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/27 19:31 linux-6.1.y 79a9660d699e 69a01293 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/27 19:31 linux-6.1.y 79a9660d699e 69a01293 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/27 19:31 linux-6.1.y 79a9660d699e 69a01293 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/12 07:44 linux-6.1.y e4f7d8be268e f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/11 17:13 linux-6.1.y e4f7d8be268e 71790083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/27 08:47 linux-6.1.y dc5c83b7f5f8 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in nfsd_shutdown_threads
* Struck through repros no longer work on HEAD.