KASAN: slab-use-after-free Read in nfsd_svc

Status: upstream: reported on 2026/07/27 23:12
Reported-by: syzbot+c0081e36d956ba121a48@syzkaller.appspotmail.com
First crash: 83d, last: 12d
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in nfsd_svc 19 54 1d13h 84d 0/3 upstream: reported on 2026/07/27 07:18
linux-5.15 KASAN: use-after-free Write in nfsd_svc 22 9 27d 84d 0/3 upstream: reported on 2026/07/27 22:56

Sample crash report:
svc: failed to register nfsdv3 RPC service (errno 111).
svc: failed to register nfsaclv3 RPC service (errno 111).
==================================================================
BUG: KASAN: slab-use-after-free in nfsd_svc+0x99a/0xab0 fs/nfsd/nfssvc.c:818
Read of size 4 at addr ffff88805cdfcc54 by task syz.0.134/6146

CPU: 0 PID: 6146 Comm: syz.0.134 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 nfsd_svc+0x99a/0xab0 fs/nfsd/nfssvc.c:818
 write_threads+0x393/0x510 fs/nfsd/nfsctl.c:417
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fbcee39e199
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fbcef2c9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fbcee625fa0 RCX: 00007fbcee39e199
RDX: 0000000000000001 RSI: 0000200000000440 RDI: 0000000000000003
RBP: 00007fbcee4358e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbcee626038 R14: 00007fbcee625fa0 R15: 00007ffe7525d0a8
 </TASK>

Allocated by task 6146:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 __svc_create+0x60/0xbb0 net/sunrpc/svc.c:520
 svc_create_pooled+0x66a/0x7e0 net/sunrpc/svc.c:618
 nfsd_create_serv+0x29f/0x5c0 fs/nfsd/nfssvc.c:672
 nfsd_svc+0x183/0xab0 fs/nfsd/nfssvc.c:801
 write_threads+0x393/0x510 fs/nfsd/nfsctl.c:417
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 6146:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 kref_put include/linux/kref.h:65 [inline]
 svc_put include/linux/sunrpc/svc.h:124 [inline]
 nfsd_svc+0x762/0xab0 fs/nfsd/nfssvc.c:816
 write_threads+0x393/0x510 fs/nfsd/nfsctl.c:417
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x900 kernel/rcu/tree.c:2837
 fib6_info_release include/net/ip6_fib.h:349 [inline]
 ip6_route_info_create+0xa0d/0x1260 net/ipv6/route.c:3891
 ip6_route_add+0x28/0x160 net/ipv6/route.c:3905
 addrconf_add_mroute net/ipv6/addrconf.c:2534 [inline]
 addrconf_add_dev+0x29c/0x3b0 net/ipv6/addrconf.c:2552
 inet6_addr_add+0x25d/0xb30 net/ipv6/addrconf.c:3032
 inet6_rtm_newaddr+0x6fd/0x9d0 net/ipv6/addrconf.c:5050
 rtnetlink_rcv_msg+0x843/0xf90 net/core/rtnetlink.c:6484
 netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 __sys_sendto+0x4a9/0x6b0 net/socket.c:2201
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0xde/0xf0 net/socket.c:2209
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805cdfcc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 84 bytes inside of
 freed 512-byte region [ffff88805cdfcc00, ffff88805cdfce00)

The buggy address belongs to the physical page:
page:ffffea0001737f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88805cdff800 pfn:0x5cdfc
head:ffffea0001737f00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c41c80 ffffea000093c700 0000000000000002
raw: ffff88805cdff800 000000008010000e 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 5779, tgid 5779 (syz-executor), ts 87697264036, free_ts 87679902589
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 devcgroup_css_alloc+0x4e/0x100 security/device_cgroup.c:226
 css_create kernel/cgroup/cgroup.c:5561 [inline]
 cgroup_apply_control_enable+0x3cc/0xb00 kernel/cgroup/cgroup.c:3219
 cgroup_mkdir+0xc83/0xe70 kernel/cgroup/cgroup.c:5779
 kernfs_iop_mkdir+0x241/0x3e0 fs/kernfs/dir.c:1246
 vfs_mkdir+0x2a5/0x470 fs/namei.c:4168
 do_mkdirat+0x1dc/0x450 fs/namei.c:4191
 __do_sys_mkdirat fs/namei.c:4206 [inline]
 __se_sys_mkdirat fs/namei.c:4204 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4204
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7d7/0x8f0 mm/page_alloc.c:2366
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2459
 __stack_depot_save+0x587/0x660 lib/stackdepot.c:443
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_set_track+0x5f/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 kmem_cache_free+0xf8/0x290 mm/slub.c:3852
 rcu_do_batch kernel/rcu/tree.c:2194 [inline]
 rcu_core+0x9c1/0x17f0 kernel/rcu/tree.c:2467
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 do_softirq+0xfa/0x1a0 kernel/softirq.c:479
 __local_bh_enable_ip+0x184/0x1c0 kernel/softirq.c:406
 addrconf_dad_completed+0xa51/0xd90 net/ipv6/addrconf.c:4371
 addrconf_dad_work+0xc9e/0x1550 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815

Memory state around the buggy address:
 ffff88805cdfcb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805cdfcb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805cdfcc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88805cdfcc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805cdfcd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (25):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/07 11:23 linux-6.6.y a91a6aa9253c 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/10/07 11:22 linux-6.6.y a91a6aa9253c 6520ecdb .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/10/07 08:14 linux-6.6.y a91a6aa9253c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/10/07 08:14 linux-6.6.y a91a6aa9253c f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/22 15:36 linux-6.6.y 79643295eba1 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/22 14:21 linux-6.6.y 79643295eba1 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/18 21:39 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/18 21:39 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/18 14:41 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/18 14:40 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/18 14:39 linux-6.6.y 79643295eba1 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 02:12 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 02:11 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 01:02 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 00:51 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 00:45 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/15 00:45 linux-6.6.y 79643295eba1 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/10 20:06 linux-6.6.y 8b73de7da85f 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/10 20:00 linux-6.6.y 8b73de7da85f 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/10 17:25 linux-6.6.y 8b73de7da85f 1fe56c0a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/09/07 23:15 linux-6.6.y 8b73de7da85f 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/08/20 22:42 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/08/20 22:42 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/08/05 01:23 linux-6.6.y aa0e49877a2e d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
2026/07/27 23:11 linux-6.6.y c5596480c50e aae9036b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in nfsd_svc
* Struck through repros no longer work on HEAD.