WARNING in sk_psock_drop

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 93ad0f96 net: wan: lapbether.c: Use built-in RCU list chec..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=132caa76e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e89bd00623fe71e
dashboard link: https://syzkaller.appspot.com/bug?extid=d73682fcf7fee6982fe3
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d73682...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 11793 at include/net/sock.h:1578 sock_owned_by_me
include/net/sock.h:1578 [inline]
WARNING: CPU: 1 PID: 11793 at include/net/sock.h:1578
sk_psock_drop+0x5fa/0x7f0 net/core/skmsg.c:597
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 11793 Comm: syz-executor.3 Not tainted 5.5.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x3e kernel/panic.c:582
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:sock_owned_by_me include/net/sock.h:1578 [inline]
RIP: 0010:sk_psock_drop+0x5fa/0x7f0 net/core/skmsg.c:597
Code: d0 7c 08 84 d2 0f 85 c7 01 00 00 44 8b 2d 22 89 4b 04 31 ff 44 89 ee
e8 f4 01 45 fb 45 85 ed 0f 84 4e fa ff ff e8 66 00 45 fb <0f> 0b e9 42 fa
ff ff e8 5a 00 45 fb 48 8d bb 70 02 00 00 48 b8 00
RSP: 0018:ffffc90001667a58 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff888098091800 RCX: ffffc900102eb000
RDX: 00000000000001a2 RSI: ffffffff862ff52a RDI: 0000000000000005
RBP: ffffc90001667aa0 R08: ffff8880a7a824c0 R09: ffffed101301234c
R10: ffffed101301234b R11: ffff888098091a5b R12: ffff8880a4606e80
R13: 0000000000000001 R14: ffff888098091800 R15: ffff8880a4606e80
sk_psock_put include/linux/skmsg.h:437 [inline]
tcp_bpf_recvmsg+0xb69/0xc90 net/ipv4/tcp_bpf.c:157
inet6_recvmsg+0x136/0x610 net/ipv6/af_inet6.c:592
sock_recvmsg_nosec net/socket.c:873 [inline]
sock_recvmsg net/socket.c:891 [inline]
sock_recvmsg+0xce/0x110 net/socket.c:887
__sys_recvfrom+0x1ff/0x350 net/socket.c:2042
__do_sys_recvfrom net/socket.c:2060 [inline]
__se_sys_recvfrom net/socket.c:2056 [inline]
__x64_sys_recvfrom+0xe1/0x1a0 net/socket.c:2056
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45aff9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f83349d7c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007f83349d86d4 RCX: 000000000045aff9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000085c R14: 00000000004c9852 R15: 000000000075bf2c
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[John Fastabend]

syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 93ad0f96 net: wan: lapbether.c: Use built-in RCU list chec..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=132caa76e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=7e89bd00623fe71e
> dashboard link: https://syzkaller.appspot.com/bug?extid=d73682fcf7fee6982fe3
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d73682...@syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 11793 at include/net/sock.h:1578 sock_owned_by_me
> include/net/sock.h:1578 [inline]
> WARNING: CPU: 1 PID: 11793 at include/net/sock.h:1578
> sk_psock_drop+0x5fa/0x7f0 net/core/skmsg.c:597
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 11793 Comm: syz-executor.3 Not tainted 5.5.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011

I recently added this sock_owned_by_me so I'll take a look. Thanks for
the report. Seems we have a case where its not held.