Re: [syzbot] [cgroups?] possible deadlock in task_rq_lock

[syzbot <syzbot+ca14b36a46a8c541b509@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in __alloc_workqueue

workqueue: Failed to create a rescuer kthread for wq "wg-crypt-\x18": -EINTR
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 6468 Comm: syz-executor Not tainted 6.11.0-rc3-next-20240816-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:__lock_acquire+0x69/0x2040 kernel/locking/lockdep.c:5010
Code: b6 04 30 84 c0 0f 85 87 16 00 00 45 31 f6 83 3d 48 05 a9 0e 00 0f 84 ac 13 00 00 89 54 24 54 89 5c 24 68 4c 89 f8 48 c1 e8 03 <80> 3c 30 00 74 12 4c 89 ff e8 49 5c 8c 00 48 be 00 00 00 00 00 fc
RSP: 0018:ffffc9000438ec30 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff20318b6 R12: ffff88802b189e00
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS:  000055556e398500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555911bd808 CR3: 00000000702f8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5762
 touch_wq_lockdep_map kernel/workqueue.c:3876 [inline]
 __flush_workqueue+0x1e3/0x1770 kernel/workqueue.c:3918
 drain_workqueue+0xc9/0x3a0 kernel/workqueue.c:4082
 destroy_workqueue+0xba/0xc40 kernel/workqueue.c:5830
 __alloc_workqueue+0x1c30/0x1fb0 kernel/workqueue.c:5745
 alloc_workqueue+0xd6/0x210 kernel/workqueue.c:5758
 wg_newlink+0x260/0x640 drivers/net/wireguard/device.c:343
 rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
 rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743
 rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6647
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 __sys_sendto+0x3a8/0x500 net/socket.c:2204
 __do_sys_sendto net/socket.c:2216 [inline]
 __se_sys_sendto net/socket.c:2212 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2212
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f52c6b7bd0c
Code: 2a 5a 02 00 44 8b 4c 24 2c 4c 8b 44 24 20 89 c5 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 34 89 ef 48 89 44 24 08 e8 70 5a 02 00 48 8b
RSP: 002b:00007ffdb7bbca90 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f52c7844620 RCX: 00007f52c6b7bd0c
RDX: 000000000000003c RSI: 00007f52c7844670 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffdb7bbcae4 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f52c7844670 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__lock_acquire+0x69/0x2040 kernel/locking/lockdep.c:5010
Code: b6 04 30 84 c0 0f 85 87 16 00 00 45 31 f6 83 3d 48 05 a9 0e 00 0f 84 ac 13 00 00 89 54 24 54 89 5c 24 68 4c 89 f8 48 c1 e8 03 <80> 3c 30 00 74 12 4c 89 ff e8 49 5c 8c 00 48 be 00 00 00 00 00 fc
RSP: 0018:ffffc9000438ec30 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff20318b6 R12: ffff88802b189e00
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS:  000055556e398500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555911bd808 CR3: 00000000702f8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	b6 04                	mov    $0x4,%dh
   2:	30 84 c0 0f 85 87 16 	xor    %al,0x1687850f(%rax,%rax,8)
   9:	00 00                	add    %al,(%rax)
   b:	45 31 f6             	xor    %r14d,%r14d
   e:	83 3d 48 05 a9 0e 00 	cmpl   $0x0,0xea90548(%rip)        # 0xea9055d
  15:	0f 84 ac 13 00 00    	je     0x13c7
  1b:	89 54 24 54          	mov    %edx,0x54(%rsp)
  1f:	89 5c 24 68          	mov    %ebx,0x68(%rsp)
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 30 00          	cmpb   $0x0,(%rax,%rsi,1) <-- trapping instruction
  2e:	74 12                	je     0x42
  30:	4c 89 ff             	mov    %r15,%rdi
  33:	e8 49 5c 8c 00       	call   0x8c5c81
  38:	48                   	rex.W
  39:	be 00 00 00 00       	mov    $0x0,%esi
  3e:	00 fc                	add    %bh,%ah


Tested on:

commit:         367b5c3d Add linux-next specific files for 20240816
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1191c45b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=61ba6f3b22ee5467
dashboard link: https://syzkaller.appspot.com/bug?extid=ca14b36a46a8c541b509
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16a7edf5980000