linux-kernel - WARNING in debug_mutex

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Date:   Mon,  9 Jan 2023 15:44:25 +0800
From:   Hao Sun <sunhao.th@...il.com>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, davem@...emloft.net,
        linux-kernel@...r.kernel.org, Hao Sun <sunhao.th@...il.com>
Subject: WARNING in debug_mutex_unlock

Hi,

The following warning can be triggered with the C reproducer in
the link. The repro starts 32 threads, each attaches a tracepoint
into `ext4_mark_inode_dirty`. The prog loads the following insns
that simply sends signal to current proc, and then wait.

Seems issues in queued irq_work with `do_bpf_send_signal`, also
I'm wondering what if the task in `send_signal_irq_work` exited,
at the time the callback invoked.

This can be reproduced on:

HEAD commit:    6d0c4b11e743 ("libbpf: Poison strlcpy()")
git tree:       bpf-next
console output: https://pastebin.com/raw/ZtVM15Jx
kernel config : https://pastebin.com/raw/nt6XW0Sz
C reproducer  : https://pastebin.com/raw/NHqy5tR6

func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (18) r0 = 0x0                      ; R0_w=0
2: (18) r6 = 0x0                      ; R6_w=0
4: (18) r7 = 0x0                      ; R7_w=0
6: (18) r8 = 0x0                      ; R8_w=0
8: (18) r9 = 0x0                      ; R9_w=0
10: (18) r1 = 0x700000007             ; R1_w=30064771079
12: (85) call bpf_send_signal#109     ; R0_w=scalar()
13: (95) exit
processed 8 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(lock->magic != lock)
WARNING: CPU: 3 PID: 41309 at kernel/locking/mutex-debug.c:74 debug_mutex_unlock+0x1fc/0x250 kernel/locking/mutex-debug.c:74
Modules linked in:
CPU: 3 PID: 41309 Comm: systemd-udevd Not tainted 6.2.0-rc2-00302-g6d0c4b11e743 #153
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
RIP: 0010:debug_mutex_unlock+0x1fc/0x250 kernel/locking/mutex-debug.c:74
Code: 84 c0 75 59 8b 15 34 92 3a 11 85 d2 0f 84 c5 fe ff ff e9 e6 fe ff ff 48 c7 c6 a0 50 4c 8a 48 c7 c7 a0 4e 4c 8a e8 9e bb 5f 08 <0f> 0b eb b2 e8 bb 9d 6e 00 e9 be fe ff ff e8 b1 9d 6e 00 e9 8b fe
RSP: 0018:ffffc90012b7f6f8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff88804145a2d0 RCX: 0000000000000000
RDX: ffff88803f468000 RSI: ffffffff81671400 RDI: fffff5200256fed1
RBP: ffffffff929e2a00 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000001 R11: ffffffff90d3f0c3 R12: ffff88804145a2d8
R13: fffffbfff253c540 R14: ffffffff929e2a00 R15: ffffc90012b7f798
FS:  00007f36a937e8c0(0000) GS:ffff888135c80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056181882c020 CR3: 000000002a9a2000 CR4: 0000000000750ee0
PKRU: 55555554
Call Trace:
 <TASK>
 __mutex_unlock_slowpath+0x197/0x630 kernel/locking/mutex.c:933
 devlink_compat_running_version+0x128/0x6c0 net/devlink/leftover.c:12237
 dev_ethtool+0x55f/0x53c0 net/ethtool/ioctl.c:3091
 dev_ioctl+0x29e/0x1050 net/core/dev_ioctl.c:524
 sock_do_ioctl+0x1be/0x250 net/socket.c:1183
 sock_ioctl+0x205/0x6a0 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+0x189/0x210 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f36a94a55f7
Code: 00 00 00 48 8b 05 99 c8 0d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 69 c8 0d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd663b3d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00005618188043f0 RCX: 00007f36a94a55f7
RDX: 00007ffd663b3e60 RSI: 0000000000008946 RDI: 0000000000000006
RBP: 00007ffd663b3e90 R08: 0000561818887fa0 R09: 0000000000000000
R10: 00007f36a937e6c0 R11: 0000000000000246 R12: 0000561818887fa0
R13: 0000561818832c70 R14: 00007ffd663b3e60 R15: 0000000000000007
 </TASK>