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

Status: upstream: reported C repro on 2026/02/15 20:21
Subsystems: bpf net
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+9307c991a6d07ce6e6d8@syzkaller.appspotmail.com
First crash: 125d, last: 112d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
1834ef72-1bc6-43af-b722-86f739663495 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-use-after-free Read in sk_msg_recvmsg 2026/06/01 09:49 2026/06/01 09:49 2026/06/01 10:42 6b4a844333e83556da95d61d7f207e7ef5cd4bc6
13d413fe-8d02-4c10-b197-9451724793e2 assessment-security 💥 KASAN: slab-use-after-free Read in sk_msg_recvmsg 2026/05/15 11:04 2026/05/15 11:04 2026/05/15 11:04 9cd3beaadf14b3a22d15fd97a0bf081ee41ebe01 failed to run ["git" "pull" "origin" "HEAD" "--depth=1" "--allow-unrelated-histories"]: exit status 1 fatal: write error: No space left on device fatal: fetch-pack: invalid index-pack output
▶ ▼ Discussions (5)
Title Replies (including bot) Last reply
[PATCH v4 bpf/net 3/6] sockmap: Fix use-after-free in udp_bpf_recvmsg(). 6 (6) 2026/03/05 17:46
[PATCH v3 bpf/net 3/6] sockmap: Fix use-after-free in udp_bpf_recvmsg(). 1 (1) 2026/02/19 17:37
[PATCH v2 bpf/net 3/6] sockmap: Fix use-after-free in udp_bpf_recvmsg(). 1 (1) 2026/02/17 00:05
[syzbot] [bpf?] [net?] KASAN: slab-use-after-free Read in sk_msg_recvmsg 2 (5) 2026/02/16 05:36
[PATCH v1 bpf/net 3/6] sockmap: Fix use-after-free in udp_bpf_recvmsg(). 1 (1) 2026/02/15 20:41
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel NULL pointer dereference in sk_msg_recvmsg net bpf 10 C 108 692d 950d 0/29 auto-obsoleted due to no activity on 2024/09/19 08:22
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/05/21 16:36 1h00m retest repro net log
2026/05/21 16:24 25m retest repro net log
2026/02/25 02:08 20m retest repro net report log
2026/02/16 05:16 18m hdanton@sina.com patch net report log
2026/02/16 00:59 43m hdanton@sina.com patch net error
2026/01/29 09:34 26m kuniyu@google.com patch net OK log
2026/01/29 09:12 26m kuniyu@google.com patch net OK log
2026/01/29 06:05 20m kuniyu@google.com patch net report log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in sk_msg_recvmsg+0xb54/0xc30 net/core/skmsg.c:428
Read of size 4 at addr ffff88814cdcf000 by task syz.0.24/6020

CPU: 1 UID: 0 PID: 6020 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 sk_msg_recvmsg+0xb54/0xc30 net/core/skmsg.c:428
 udp_bpf_recvmsg+0x4bd/0xe00 net/ipv4/udp_bpf.c:84
 inet_recvmsg+0x260/0x270 net/ipv4/af_inet.c:891
 sock_recvmsg_nosec net/socket.c:1078 [inline]
 sock_recvmsg+0x1a8/0x270 net/socket.c:1100
 ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2812
 ___sys_recvmsg+0x215/0x590 net/socket.c:2854
 do_recvmmsg+0x334/0x800 net/socket.c:2949
 __sys_recvmmsg net/socket.c:3023 [inline]
 __do_sys_recvmmsg net/socket.c:3046 [inline]
 __se_sys_recvmmsg net/socket.c:3039 [inline]
 __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3039
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb319f9aeb9
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:00007fb31ad97028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007fb31a216090 RCX: 00007fb319f9aeb9
RDX: 0000000000000001 RSI: 0000200000000400 RDI: 0000000000000004
RBP: 00007fb31a008c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000040000021 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb31a216128 R14: 00007fb31a216090 R15: 00007ffe21dd0a98
 </TASK>

Allocated by task 6019:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3d1/0x6e0 mm/slub.c:5780
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 alloc_sk_msg net/core/skmsg.c:510 [inline]
 sk_psock_skb_ingress_self+0x60/0x350 net/core/skmsg.c:612
 sk_psock_verdict_apply net/core/skmsg.c:1038 [inline]
 sk_psock_verdict_recv+0x7d9/0x8d0 net/core/skmsg.c:1236
 udp_read_skb+0x73e/0x7e0 net/ipv4/udp.c:2045
 sk_psock_verdict_data_ready+0x12d/0x550 net/core/skmsg.c:1257
 __udp_enqueue_schedule_skb+0xc54/0x10b0 net/ipv4/udp.c:1789
 __udp_queue_rcv_skb net/ipv4/udp.c:2346 [inline]
 udp_queue_rcv_one_skb+0xac5/0x19c0 net/ipv4/udp.c:2475
 __udp4_lib_mcast_deliver+0xc06/0xcf0 net/ipv4/udp.c:2585
 __udp4_lib_rcv+0x10f6/0x2620 net/ipv4/udp.c:2724
 ip_protocol_deliver_rcu+0x282/0x440 net/ipv4/ip_input.c:207
 ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:241
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 dst_input include/net/dst.h:474 [inline]
 ip_sublist_rcv_finish+0x221/0x2a0 net/ipv4/ip_input.c:584
 ip_list_rcv_finish net/ipv4/ip_input.c:628 [inline]
 ip_sublist_rcv+0x5c6/0xa70 net/ipv4/ip_input.c:644
 ip_list_rcv+0x3f1/0x450 net/ipv4/ip_input.c:678
 __netif_receive_skb_list_ptype net/core/dev.c:6195 [inline]
 __netif_receive_skb_list_core+0x7e5/0x810 net/core/dev.c:6242
 __netif_receive_skb_list net/core/dev.c:6294 [inline]
 netif_receive_skb_list_internal+0x995/0xcf0 net/core/dev.c:6385
 netif_receive_skb_list+0x54/0x410 net/core/dev.c:6437
 xdp_recv_frames net/bpf/test_run.c:269 [inline]
 xdp_test_run_batch net/bpf/test_run.c:350 [inline]
 bpf_test_run_xdp_live+0x1946/0x1cf0 net/bpf/test_run.c:379
 bpf_prog_test_run_xdp+0x81c/0x1160 net/bpf/test_run.c:1396
 bpf_prog_test_run+0x2c7/0x340 kernel/bpf/syscall.c:4703
 __sys_bpf+0x5cb/0x920 kernel/bpf/syscall.c:6182
 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6272
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6021:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6674 [inline]
 kfree+0x1be/0x650 mm/slub.c:6882
 kfree_sk_msg include/linux/skmsg.h:385 [inline]
 sk_msg_recvmsg+0xaa8/0xc30 net/core/skmsg.c:483
 udp_bpf_recvmsg+0x4bd/0xe00 net/ipv4/udp_bpf.c:84
 inet_recvmsg+0x260/0x270 net/ipv4/af_inet.c:891
 sock_recvmsg_nosec net/socket.c:1078 [inline]
 sock_recvmsg+0x1a8/0x270 net/socket.c:1100
 ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2812
 ___sys_recvmsg+0x215/0x590 net/socket.c:2854
 do_recvmmsg+0x334/0x800 net/socket.c:2949
 __sys_recvmmsg net/socket.c:3023 [inline]
 __do_sys_recvmmsg net/socket.c:3046 [inline]
 __se_sys_recvmmsg net/socket.c:3039 [inline]
 __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3039
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88814cdcf000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of
 freed 1024-byte region [ffff88814cdcf000, ffff88814cdcf400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14cdc8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88813fe26dc0 ffffea000509f800 dead000000000002
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff88813fe26dc0 ffffea000509f800 dead000000000002
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 057ff00000000003 ffffea0005337201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 17135672743, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
 prep_new_page mm/page_alloc.c:1892 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3a0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xd82/0x1760 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __kmalloc_cache_noprof+0x40d/0x6e0 mm/slub.c:5775
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 init_srcu_struct_fields+0x7f/0xa20 kernel/rcu/srcutree.c:240
 rtnl_link_register+0x141/0x2f0 net/core/rtnetlink.c:615
 ipgre_init+0x64/0x110 net/ipv4/ip_gre.c:1819
 do_one_initcall+0x250/0x840 init/main.c:1378
 do_initcall_level+0x104/0x190 init/main.c:1440
 do_initcalls+0x59/0xa0 init/main.c:1456
 kernel_init_freeable+0x2a6/0x3d0 init/main.c:1688
 kernel_init+0x1d/0x1d0 init/main.c:1578
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88814cdcef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88814cdcef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88814cdcf000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88814cdcf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88814cdcf100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/29 04:07 net a040afa3bca4 b78a7341 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: slab-use-after-free Read in sk_msg_recvmsg
2026/02/10 13:06 upstream 72c395024dac a076df6f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-use-after-free Read in sk_msg_recvmsg
2026/01/28 21:39 net a040afa3bca4 004c195c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce KASAN: slab-use-after-free Read in sk_msg_recvmsg
* Struck through repros no longer work on HEAD.