[syzbot] WARNING: refcount bug in nr_release (3)

syzbot
2021-11-18T10:37:50Z

Hello,

syzbot found the following issue on:

HEAD commit: f2e19fd15bd7 Add linux-next specific files for 20211112
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14de0821b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ba9c83199208e103
dashboard link: https://syzkaller.appspot.com/bug?extid=342c8cfbf3eb29cb36e8
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+342c8cfbf3eb29cb36e8@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 13624 at lib/refcount.c:25 refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25
Modules linked in:
CPU: 0 PID: 13624 Comm: syz-executor.4 Not tainted 5.15.0-next-20211112-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:refcount_warn_saturate+0x169/0x1e0 lib/refcount.c:25
Code: 09 31 ff 89 de e8 27 70 a0 fd 84 db 0f 85 36 ff ff ff e8 3a 6c a0 fd 48 c7 c7 a0 5f 04 8a c6 05 0e 1e a5 09 01 e8 de 4d 34 05 <0f> 0b e9 17 ff ff ff e8 1b 6c a0 fd 0f b6 1d f3 1d a5 09 31 ff 89
RSP: 0018:ffffc9000282fa70 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802c4fd7c0 RSI: ffffffff815f5c98 RDI: fffff52000505f40
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815efa3e R11: 0000000000000000 R12: ffff88803cd1c200
R13: ffff88803c3d7080 R14: ffff88803cd1c218 R15: ffff888011a4a620
FS: 0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffdbaf50df8 CR3: 0000000022a02000 CR4: 00000000003526f0
Call Trace:
<TASK>
__refcount_add include/linux/refcount.h:199 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
sock_hold include/net/sock.h:708 [inline]
nr_release+0x3d1/0x450 net/netrom/af_netrom.c:520
__sock_release+0xcd/0x280 net/socket.c:649
sock_close+0x18/0x20 net/socket.c:1314
__fput+0x286/0x9f0 fs/file_table.c:280
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0xc14/0x2b40 kernel/exit.c:832
do_group_exit+0x125/0x310 kernel/exit.c:929
get_signal+0x47d/0x2220 kernel/signal.c:2830
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f8de835cae9
Code: Unable to access opcode bytes at RIP 0x7f8de835cabf.
RSP: 002b:00007f8de58d2218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f8de846ff68 RCX: 00007f8de835cae9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f8de846ff68
RBP: 00007f8de846ff60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f8de846ff6c
R13: 00007ffc7f8041ff R14: 00007f8de58d2300 R15: 0000000000022000
</TASK>

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