syzbot


WARNING: refcount bug in sk_common_release (2)

Status: upstream: reported on 2026/04/23 13:23
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+8c9eede336e3a843750e@syzkaller.appspotmail.com
First crash: 10d, last: 4h25m
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] WARNING: refcount bug in sk_common_release (2) 0 (1) 2026/04/23 13:23
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING: refcount bug in sk_common_release net 13 C 9 640d 655d 27/29 fixed on 2024/08/26 12:53

Sample crash report:
siw: device registration error -23
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28, CPU#3: syz.6.1732/12352
Modules linked in:
CPU: 3 UID: 0 PID: 12352 Comm: syz.6.1732 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28
Code: 06 e8 50 3c 0f fd 48 8d 3d 69 cc e8 0b 67 48 0f b9 3a e8 3f 3c 0f fd 5b 5d c3 cc cc cc cc e8 33 3c 0f fd 48 8d 3d 5c cc e8 0b <67> 48 0f b9 3a e8 22 3c 0f fd 5b 5d e9 5b eb 93 06 e8 16 3c 0f fd
RSP: 0000:ffffc900264af120 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888023c84480 RCX: ffffffff84f94f1b
RDX: ffff88803550ca00 RSI: ffffffff84f94fad RDI: ffffffff90e21c10
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000003 R11: 0000000000000000 R12: ffff888023c84480
R13: ffffffff8a0507c0 R14: 0000000000000000 R15: 0000000000000018
FS:  00007fa8b6e096c0(0000) GS:ffff8880d6676000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2d423ffc CR3: 0000000031076000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 sock_put include/net/sock.h:2009 [inline]
 sk_common_release+0x260/0x370 net/core/sock.c:4024
 inet_release+0xed/0x200 net/ipv4/af_inet.c:442
 __sock_release net/socket.c:722 [inline]
 sock_release+0x91/0x1c0 net/socket.c:750
 rxe_release_udp_tunnel drivers/infiniband/sw/rxe/rxe_net.c:294 [inline]
 rxe_sock_put+0xae/0x130 drivers/infiniband/sw/rxe/rxe_net.c:639
 rxe_net_del+0x83/0x120 drivers/infiniband/sw/rxe/rxe_net.c:660
 rxe_dellink+0x15/0x20 drivers/infiniband/sw/rxe/rxe.c:254
 nldev_dellink+0x289/0x3c0 drivers/infiniband/core/nldev.c:1849
 rdma_nl_rcv_msg+0x392/0x6f0 drivers/infiniband/core/netlink.c:195
 rdma_nl_rcv_skb.constprop.0.isra.0+0x2cb/0x410 drivers/infiniband/core/netlink.c:239
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2698
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2752
 __sys_sendmsg+0x170/0x220 net/socket.c:2784
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa8b5f9cdd9
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:00007fa8b6e09028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fa8b6215fa0 RCX: 00007fa8b5f9cdd9
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 000000000000000b
RBP: 00007fa8b6032d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa8b6216038 R14: 00007fa8b6215fa0 R15: 00007ffd313b4c78
 </TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	e8 50 3c 0f fd       	call   0xfd0f3c55
   5:	48 8d 3d 69 cc e8 0b 	lea    0xbe8cc69(%rip),%rdi        # 0xbe8cc75
   c:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  11:	e8 3f 3c 0f fd       	call   0xfd0f3c55
  16:	5b                   	pop    %rbx
  17:	5d                   	pop    %rbp
  18:	c3                   	ret
  19:	cc                   	int3
  1a:	cc                   	int3
  1b:	cc                   	int3
  1c:	cc                   	int3
  1d:	e8 33 3c 0f fd       	call   0xfd0f3c55
  22:	48 8d 3d 5c cc e8 0b 	lea    0xbe8cc5c(%rip),%rdi        # 0xbe8cc85
* 29:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2e:	e8 22 3c 0f fd       	call   0xfd0f3c55
  33:	5b                   	pop    %rbx
  34:	5d                   	pop    %rbp
  35:	e9 5b eb 93 06       	jmp    0x693eb95
  3a:	e8 16 3c 0f fd       	call   0xfd0f3c55

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/04 05:01 upstream f377d0025eb0 a0d91488 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in sk_common_release
2026/05/04 00:35 upstream f377d0025eb0 a0d91488 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in sk_common_release
2026/04/23 12:31 upstream 2a4c0c11c019 b10da5ec .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING: refcount bug in sk_common_release
2026/04/26 15:13 upstream 897d54018cc9 9c2d0995 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING: refcount bug in sk_common_release
* Struck through repros no longer work on HEAD.