[syzbot] possible deadlock in strp_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8755ae45a9e8 Add linux-next specific files for 20220819
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10d3e2d3080000
kernel config: https://syzkaller.appspot.com/x/.config?x=ead6107a3bbe3c62
dashboard link: https://syzkaller.appspot.com/bug?extid=9fc084a4348493ef65d2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1136b1a5080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10bb167b080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9fc084...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc1-next-20220819-syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:2/38 is trying to acquire lock:
ffff888026598d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: do_strp_work net/strparser/strparser.c:398 [inline]
ffff888026598d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: strp_work+0x40/0x130 net/strparser/strparser.c:415

but task is already holding lock:
ffffc90000af7da8 ((work_completion)(&strp->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((work_completion)(&strp->work)){+.+.}-{0:0}:
__flush_work+0x105/0xae0 kernel/workqueue.c:3069
__cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
strp_done+0x64/0xf0 net/strparser/strparser.c:513
kcm_attach net/kcm/kcmsock.c:1429 [inline]
kcm_attach_ioctl net/kcm/kcmsock.c:1490 [inline]
kcm_ioctl+0x913/0x1180 net/kcm/kcmsock.c:1696
sock_do_ioctl+0xcc/0x230 net/socket.c:1169
sock_ioctl+0x2f1/0x640 net/socket.c:1286
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (sk_lock-AF_INET){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
lock_acquire kernel/locking/lockdep.c:5666 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
lock_sock_nested+0x36/0xf0 net/core/sock.c:3391
do_strp_work net/strparser/strparser.c:398 [inline]
strp_work+0x40/0x130 net/strparser/strparser.c:415
process_one_work+0x991/0x1610 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock((work_completion)(&strp->work));
lock(sk_lock-AF_INET);
lock((work_completion)(&strp->work));
lock(sk_lock-AF_INET);

*** DEADLOCK ***

2 locks held by kworker/u4:2/38:
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline]
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline]
#0: ffff88802642d138 ((wq_completion)kstrp){+.+.}-{0:0}, at: process_one_work+0x87a/0x1610 kernel/workqueue.c:2260
#1: ffffc90000af7da8 ((work_completion)(&strp->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

stack backtrace:
CPU: 1 PID: 38 Comm: kworker/u4:2 Not tainted 6.0.0-rc1-next-20220819-syzkaller #0
kworker/u4:2[38] cmdline: ��a�����
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Workqueue: kstrp strp_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:122 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:140
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
lock_acquire kernel/locking/lockdep.c:5666 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
lock_sock_nested+0x36/0xf0 net/core/sock.c:3391
do_strp_work net/strparser/strparser.c:398 [inline]
strp_work+0x40/0x130 net/strparser/strparser.c:415
process_one_work+0x991/0x1610 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>


---
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syzbot can test patches for this issue, for details see:
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[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+9fc084...@syzkaller.appspotmail.com

Tested on:

commit: e82c649e Revert "net: macsec: update SCI upon MAC addr..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=17fcd6f3080000
kernel config: https://syzkaller.appspot.com/x/.config?x=3b9175e0879a7749

dashboard link: https://syzkaller.appspot.com/bug?extid=9fc084a4348493ef65d2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=173479e3080000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+9fc084...@syzkaller.appspotmail.com

Tested on:

commit: b86437b4 kcm: get rid of unnecessary cleanup
git tree: https://github.com/congwang/linux.git net
console output: https://syzkaller.appspot.com/x/log.txt?x=11584bad080000
kernel config: https://syzkaller.appspot.com/x/.config?x=911efaff115942bb

dashboard link: https://syzkaller.appspot.com/bug?extid=9fc084a4348493ef65d2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.