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: 29d, last: 12h04m
▶ ▼ 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 4 5d01h 29d 0/2 upstream: reported on 2026/07/27 23:12
linux-5.15 KASAN: use-after-free Write in nfsd_svc 22 4 4d15h 29d 0/3 upstream: reported on 2026/07/27 22:56

Sample crash report:
svc: failed to register nfsaclv3 RPC service (errno 111).
==================================================================
BUG: KASAN: use-after-free in nfsd_svc+0x996/0xab0 fs/nfsd/nfssvc.c:813
Read of size 4 at addr ffff88802776a454 by task syz.2.275/5595

CPU: 1 PID: 5595 Comm: syz.2.275 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
 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: 0033:0x7fd49059e0d9
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:00007fd4914ee028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd490825fa0 RCX: 00007fd49059e0d9
RDX: 0000000000000002 RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007fd490635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd490826038 R14: 00007fd490825fa0 R15: 00007ffcbd715ee8
 </TASK>

Allocated by task 5595:
 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
 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 5595:
 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 ffff88802776a400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 84 bytes inside of
 512-byte region [ffff88802776a400, ffff88802776a600)

The buggy address belongs to the physical page:
page:ffffea00009dda00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27768
head:ffffea00009dda00 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4278, tgid 4278 (syz-executor), ts 88541738507, free_ts 82399275381
 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_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]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
 netlink_sendmsg+0x654/0xbd0 net/netlink/af_netlink.c:1852
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 __sys_sendto+0x497/0x650 net/socket.c:2153
 __do_sys_sendto net/socket.c:2165 [inline]
 __se_sys_sendto net/socket.c:2161 [inline]
 __x64_sys_sendto+0xda/0xf0 net/socket.c:2161
 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
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
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 __kmem_cache_alloc_node+0x19d/0x270 mm/slub.c:3398
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 ref_tracker_alloc+0x14f/0x490 lib/ref_tracker.c:85
 __netdev_tracker_alloc include/linux/netdevice.h:4044 [inline]
 netdev_hold include/linux/netdevice.h:4073 [inline]
 rx_queue_add_kobject net/core/net-sysfs.c:1058 [inline]
 net_rx_queue_update_kobjects+0x164/0x4d0 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:10243
 veth_newlink+0x66a/0xd60 drivers/net/veth.c:1739
 rtnl_newlink_create net/core/rtnetlink.c:3436 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3656 [inline]
 rtnl_newlink+0x14b3/0x1f90 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

Memory state around the buggy address:
 ffff88802776a300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802776a380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802776a400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88802776a480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802776a500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (26):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
2026/08/21 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
* Struck through repros no longer work on HEAD.