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: 13d, last: 2d20h
▶ ▼ 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 484 22h36m 13d 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 7 4d20h 12d 0/2 upstream: reported 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 ffff888058b7d050 by task syz-executor/4277

CPU: 1 PID: 4277 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5012b9f317
Code: a2 c7 05 dc 43 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:00007fffbdc79308 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f5012c34474 RCX: 00007f5012b9f317
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fffbdc793c0
RBP: 00007fffbdc793c0 R08: 00007fffbdc7a3c0 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffbdc7a450
R13: 00007f5012c34474 R14: 000000000001cf1c R15: 00007fffbdc7a490
 </TASK>

Allocated by task 5048:
 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:464
 svc_create_pooled+0x71f/0x8c0 net/sunrpc/svc.c:552
 nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:667
 __write_ports_addxprt fs/nfsd/nfsctl.c:750 [inline]
 __write_ports fs/nfsd/nfsctl.c:794 [inline]
 write_ports+0x560/0xb80 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 5048:
 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:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 __kmem_cache_free+0xb6/0x200 mm/slub.c:3700
 kref_put include/linux/kref.h:65 [inline]
 svc_put include/linux/sunrpc/svc.h:123 [inline]
 __write_ports_addxprt fs/nfsd/nfsctl.c:780 [inline]
 __write_ports fs/nfsd/nfsctl.c:794 [inline]
 write_ports+0x924/0xb80 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 ffff888058b7d000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 80 bytes inside of
 512-byte region [ffff888058b7d000, ffff888058b7d200)

The buggy address belongs to the physical page:
page:ffffea000162df00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x58b7c
head:ffffea000162df00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888017441c80
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 0x52a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 4271, tgid 4271 (syz-executor), ts 80515388343, free_ts 80477620055
 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:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:1997
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa3/0x240 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 switchdev_deferred_enqueue+0x2d/0x240 net/switchdev/switchdev.c:117
 switchdev_port_attr_set_defer net/switchdev/switchdev.c:183 [inline]
 switchdev_port_attr_set+0xfb/0x2d0 net/switchdev/switchdev.c:202
 br_set_state+0x374/0x690 net/bridge/br_stp.c:52
 br_init_port+0x95/0x200 net/bridge/br_stp_if.c:39
 new_nbp+0x2f3/0x430 net/bridge/br_if.c:446
 br_add_if+0x27c/0xee0 net/bridge/br_if.c:603
 do_set_master net/core/rtnetlink.c:2642 [inline]
 do_setlink+0xd66/0x29c0 net/core/rtnetlink.c:2852
 __rtnl_newlink net/core/rtnetlink.c:3622 [inline]
 rtnl_newlink+0x16e4/0x1f90 net/core/rtnetlink.c:3669
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
 __stack_depot_save+0x44d/0x480 lib/stackdepot.c:506
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_set_track+0x60/0x70 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]
 netdevice_queue_work drivers/infiniband/core/roce_gid_mgmt.c:643 [inline]
 netdevice_event+0x325/0x900 drivers/infiniband/core/roce_gid_mgmt.c:802
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
 call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
 call_netdevice_notifiers net/core/dev.c:2066 [inline]
 dev_open+0x10c/0x190 net/core/dev.c:1542
 team_port_add drivers/net/team/team.c:1227 [inline]
 team_add_slave+0x6bd/0x2820 drivers/net/team/team.c:2002
 do_set_master net/core/rtnetlink.c:2642 [inline]
 do_setlink+0xd66/0x29c0 net/core/rtnetlink.c:2852
 __rtnl_newlink net/core/rtnetlink.c:3622 [inline]
 rtnl_newlink+0x16e4/0x1f90 net/core/rtnetlink.c:3669
 rtnetlink_rcv_msg+0x863/0xfb0 net/core/rtnetlink.c:6166
 netlink_rcv_skb+0x1ef/0x440 net/netlink/af_netlink.c:2516
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x7ad/0x920 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8ad/0xbd0 net/netlink/af_netlink.c:1877
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 __sys_sendto+0x497/0x650 net/socket.c:2153

Memory state around the buggy address:
 ffff888058b7cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888058b7cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888058b7d000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888058b7d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888058b7d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (22):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/06 20:13 linux-6.1.y 03f3a99e8e93 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/06 20:13 linux-6.1.y 03f3a99e8e93 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/05 00:23 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/04 19:34 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/03 22:25 linux-6.1.y fb28aa725e05 6b7c9f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/03 22:05 linux-6.1.y fb28aa725e05 6b7c9f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/03 21:22 linux-6.1.y fb28aa725e05 6b7c9f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/03 21:18 linux-6.1.y fb28aa725e05 6b7c9f71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/08/03 01:50 linux-6.1.y fb28aa725e05 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in nfsd_shutdown_threads
2026/07/31 05:18 linux-6.1.y fb28aa725e05 aaffb173 .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 00:15 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 00:09 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
2026/08/06 22:35 linux-6.1.y 03f3a99e8e93 c38879ea .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
2026/08/06 16:34 linux-6.1.y fb28aa725e05 c38879ea .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
2026/08/05 06:20 linux-6.1.y fb28aa725e05 52aa2820 .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
2026/08/03 12:30 linux-6.1.y fb28aa725e05 6b7c9f71 .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
2026/08/03 12:29 linux-6.1.y fb28aa725e05 6b7c9f71 .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
2026/08/03 09:57 linux-6.1.y fb28aa725e05 e611ffe1 .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.