WARNING in aa_sock_msg_perm

WARNING in aa_sock_msg_perm

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    fcc32a21 liquidio: Use pcie_flr() instead of reimplementin..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11233726600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
dashboard link: https://syzkaller.appspot.com/bug?extid=cda1ac91660a61b51495
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+cda1ac91660a61b51495@syzkaller.appspotmail.com

------------[ cut here ]------------
AppArmor WARN aa_sock_msg_perm: ((!sock)):
WARNING: CPU: 0 PID: 11187 at security/apparmor/lsm.c:920  
aa_sock_msg_perm.isra.0+0xdd/0x170 security/apparmor/lsm.c:920
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 11187 Comm: kworker/0:5 Not tainted 5.3.0-rc3+ #124
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: krxrpcd rxrpc_peer_keepalive_worker
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  panic+0x2dc/0x755 kernel/panic.c:219
  __warn.cold+0x20/0x4c kernel/panic.c:576
  report_bug+0x263/0x2b0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:179 [inline]
  fixup_bug arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
  do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:aa_sock_msg_perm.isra.0+0xdd/0x170 security/apparmor/lsm.c:920
Code: 89 ef e8 66 e6 02 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 16 25 68 fe  
48 c7 c6 a0 8f c0 87 48 c7 c7 a0 7a c0 87 e8 db 97 39 fe <0f> 0b e9 43 ff  
ff ff e8 f7 24 68 fe 48 c7 c6 a0 8f c0 87 48 c7 c7
RSP: 0018:ffff8880689f79b0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815c3ba6 RDI: ffffed100d13ef28
RBP: ffff8880689f79d8 R08: ffff88806916e300 R09: fffffbfff11b42c5
R10: fffffbfff11b42c4 R11: ffffffff88da1623 R12: ffff8880689f7b20
R13: ffffffff87c07ee0 R14: 0000000000000002 R15: 000000000000001d
  apparmor_socket_sendmsg+0x2a/0x30 security/apparmor/lsm.c:936
  security_socket_sendmsg+0x77/0xc0 security/security.c:1973
  sock_sendmsg+0x45/0x130 net/socket.c:654
  kernel_sendmsg+0x44/0x50 net/socket.c:677
  rxrpc_send_keepalive+0x1ff/0x940 net/rxrpc/output.c:656
  rxrpc_peer_keepalive_dispatch net/rxrpc/peer_event.c:369 [inline]
  rxrpc_peer_keepalive_worker+0x7be/0xd02 net/rxrpc/peer_event.c:430
  process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
  worker_thread+0x98/0xe40 kernel/workqueue.c:2415
  kthread+0x361/0x430 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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Re: WARNING in aa_sock_msg_perm

[Tetsuo Handa]

On 2019/08/12 21:30, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    fcc32a21 liquidio: Use pcie_flr() instead of reimplementin..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=11233726600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
> dashboard link: https://syzkaller.appspot.com/bug?extid=cda1ac91660a61b51495
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

> ------------[ cut here ]------------
> AppArmor WARN aa_sock_msg_perm: ((!sock)):

This is not AppArmor's bug. LSM modules expect that "struct socket" is not NULL.
For some reason, peer->local->socket became NULL. Thus, suspecting rxrpc's bug.

>  rxrpc_send_keepalive+0x1ff/0x940 net/rxrpc/output.c:656

Re: WARNING in aa_sock_msg_perm

[David Howells]

Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:

> This is not AppArmor's bug. LSM modules expect that "struct socket" is not
> NULL.  For some reason, peer->local->socket became NULL. Thus, suspecting
> rxrpc's bug.
> 
> >  rxrpc_send_keepalive+0x1ff/0x940 net/rxrpc/output.c:656

I agree.  There's a further refcounting bug in the local object handling, but
it's proving annoyingly difficult to reliably reproduce.

David