KASAN: use-after-free Read in nfsd_svc

Status: upstream: reported on 2026/07/27 07:18
Reported-by: syzbot+58b170c28cb18dcbe370@syzkaller.appspotmail.com
First crash: 84d, last: 1d12h
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 KASAN: slab-use-after-free Read in nfsd_svc 19 25 12d 83d 0/2 upstream: reported on 2026/07/27 23:12
linux-5.15 KASAN: use-after-free Write in nfsd_svc 22 9 27d 83d 0/3 upstream: reported on 2026/07/27 22:56

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in nfsd_svc+0x996/0xab0 fs/nfsd/nfssvc.c:813
Read of size 4 at addr ffff888055558854 by task syz.0.162/4833

CPU: 0 PID: 4833 Comm: syz.0.162 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
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
 nfsd_svc+0x996/0xab0 fs/nfsd/nfssvc.c:813
 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424
 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
RIP: 0033:0x7f556099e559
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:00007f5561883028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5560c25fa0 RCX: 00007f556099e559
RDX: 0000000000000001 RSI: 0000200000000240 RDI: 0000000000000004
RBP: 00007f5560a35ab8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5560c26038 R14: 00007f5560c25fa0 R15: 00007ffef304e2b8
 </TASK>

Allocated by task 4833:
 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
 nfsd_svc+0x17f/0xab0 fs/nfsd/nfssvc.c:796
 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424
 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 4833:
 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]
 nfsd_svc+0x75e/0xab0 fs/nfsd/nfssvc.c:811
 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424
 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 ffff888055558800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 84 bytes inside of
 512-byte region [ffff888055558800, ffff888055558a00)

The buggy address belongs to the physical page:
page:ffffea0001555600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x55558
head:ffffea0001555600 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 4276, tgid 4276 (syz-executor), ts 89626415917, free_ts 26756582025
 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]
 kzalloc include/linux/slab.h:699 [inline]
 fib6_info_alloc+0x2e/0xe0 net/ipv6/ip6_fib.c:156
 ip6_route_info_create+0x455/0x1220 net/ipv6/route.c:3800
 addrconf_f6i_alloc+0x1ec/0x430 net/ipv6/route.c:4627
 ipv6_add_addr+0x461/0xfc0 net/ipv6/addrconf.c:1121
 inet6_addr_add+0x43e/0x9c0 net/ipv6/addrconf.c:3028
 inet6_rtm_newaddr+0x6c9/0x8f0 net/ipv6/addrconf.c:4988
 rtnetlink_rcv_msg+0x863/0xfb0 net/core/rtnetlink.c:6166
 netlink_rcv_skb+0x1ef/0x440 net/netlink/af_netlink.c:2516
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:9498
 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:
 ffff888055558700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888055558780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888055558800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888055558880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888055558900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (54):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/18 09:08 linux-6.1.y 79807e970724 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/10/06 02:37 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 Read in nfsd_svc
2026/10/05 05:32 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 Read in nfsd_svc
2026/10/01 00:59 linux-6.1.y 1a8763b93150 38f7f0d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/09/22 12:31 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 Read in nfsd_svc
2026/09/22 11:45 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 Read in nfsd_svc
2026/09/22 11:32 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 Read in nfsd_svc
2026/09/17 15:59 linux-6.1.y 1a8763b93150 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/09/15 00:45 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 Read in nfsd_svc
2026/09/15 00:44 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 Read in nfsd_svc
2026/09/15 00:19 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 Read in nfsd_svc
2026/09/15 00:19 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 Read in nfsd_svc
2026/09/15 00:18 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 Read in nfsd_svc
2026/09/07 22:18 linux-6.1.y cf82dcca9634 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/08/25 11:42 linux-6.1.y 05208478041c 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/08/25 11:42 linux-6.1.y 05208478041c 614e416a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in nfsd_svc
2026/08/19 07:27 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 Read in nfsd_svc
2026/08/17 18:14 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 Read in nfsd_svc
2026/08/17 18:05 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 Read in nfsd_svc
2026/08/07 00:22 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 Read in nfsd_svc
2026/08/05 01:48 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 Read in nfsd_svc
2026/08/04 22:13 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 Read in nfsd_svc
2026/08/04 22:12 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 Read in nfsd_svc
2026/08/03 22:00 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 Read in nfsd_svc
2026/08/03 21:59 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 Read in nfsd_svc
2026/08/03 21:38 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 Read in nfsd_svc
2026/07/28 00:27 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 Read in nfsd_svc
2026/07/28 00:23 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 Read in nfsd_svc
2026/07/27 23:44 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 Read in nfsd_svc
2026/10/18 07:50 linux-6.1.y 79807e970724 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/10/06 07:52 linux-6.1.y a500ba24937a f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/10/05 23:16 linux-6.1.y a500ba24937a af63e995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/09/30 15:19 linux-6.1.y 1a8763b93150 7808aef4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/09/22 12:34 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 Read in nfsd_svc
2026/09/17 23:41 linux-6.1.y 1a8763b93150 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/09/17 23:35 linux-6.1.y 1a8763b93150 8d7d05f1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/09/17 11:16 linux-6.1.y 1a8763b93150 95928915 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/09/14 22:12 linux-6.1.y 1a8763b93150 81a27d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/21 08:25 linux-6.1.y 7e6e67054721 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/17 08:35 linux-6.1.y e4f7d8be268e 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/17 08:05 linux-6.1.y e4f7d8be268e 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 21:33 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 20:49 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 20:49 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 20:48 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 19:54 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/08/04 19:43 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/07/28 08:45 linux-6.1.y dc5c83b7f5f8 45ae1df4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in nfsd_svc
2026/07/27 07:17 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 Read in nfsd_svc
2026/09/22 12:40 linux-6.1.y 1a8763b93150 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KFENCE: use-after-free read in nfsd_svc
* Struck through repros no longer work on HEAD.