[syzbot] [kernel?] WARNING in driver_unregister (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c435a4f487e8 Merge tag 'riscv-for-linus-6.16-rc5' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138f8f70580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5ba6cef8f153bfeb
dashboard link: https://syzkaller.appspot.com/bug?extid=6616bba359cec7a1def1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b8febc580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=118f6c8c580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c435a4f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/691cd7284e87/vmlinux-c435a4f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e61b1a511aab/bzImage-c435a4f4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6616bb...@syzkaller.appspotmail.com

Unexpected driver unregister!
WARNING: CPU: 1 PID: 6119 at drivers/base/driver.c:273 driver_unregister drivers/base/driver.c:273 [inline]
WARNING: CPU: 1 PID: 6119 at drivers/base/driver.c:273 driver_unregister+0x90/0xb0 drivers/base/driver.c:270
Modules linked in:
CPU: 1 UID: 0 PID: 6119 Comm: syz.0.16 Not tainted 6.16.0-rc4-syzkaller-00286-gc435a4f487e8 #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:driver_unregister drivers/base/driver.c:273 [inline]
RIP: 0010:driver_unregister+0x90/0xb0 drivers/base/driver.c:270
Code: 48 89 ef e8 12 8f 55 fc 48 89 df e8 7a 93 ff ff 5b 5d e9 63 cf ae fb e8 5e cf ae fb 90 48 c7 c7 80 ef 41 8c e8 91 8f 6d fb 90 <0f> 0b 90 90 5b 5d e9 45 cf ae fb e8 40 ab 15 fc eb 94 e8 39 ab 15
RSP: 0018:ffffc900049d79d8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffffffff90173840 RCX: ffffffff817ae278
RDX: ffff888029d50000 RSI: ffffffff817ae285 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000002
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888107f6b800
FS: 000055555b4fa500(0000) GS:ffff8880d6815000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e55ffff CR3: 000000002b847000 CR4: 0000000000352ef0
Call Trace:
<TASK>
comedi_device_detach+0x13d/0x9e0 drivers/comedi/drivers.c:207
comedi_device_attach+0x43d/0x900 drivers/comedi/drivers.c:1000
do_devconfig_ioctl+0x1a7/0x580 drivers/comedi/comedi_fops.c:855
comedi_unlocked_ioctl+0x15bb/0x2e90 drivers/comedi/comedi_fops.c:2136
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f587658e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff8eccbf98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f58767b5fa0 RCX: 00007f587658e929
RDX: 0000200000000080 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007f5876610b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f58767b5fa0 R14: 00007f58767b5fa0 R15: 0000000000000003
</TASK>


---
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If you want to undo deduplication, reply with:
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[Hillf Danton]

> Date: Fri, 04 Jul 2025 20:20:34 -0700

> syzbot found the following issue on:
>
> HEAD commit: c435a4f487e8 Merge tag 'riscv-for-linus-6.16-rc5' of git:/..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=138f8f70580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5ba6cef8f153bfeb
> dashboard link: https://syzkaller.appspot.com/bug?extid=6616bba359cec7a1def1
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b8febc580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=118f6c8c580000

#syz test

--- x/drivers/comedi/drivers.c
+++ y/drivers/comedi/drivers.c
@@ -994,10 +994,13 @@ int comedi_device_attach(struct comedi_d
dev->board_name = dev->board_ptr ? *(const char **)dev->board_ptr
: dev->driver->driver_name;
ret = driv->attach(dev, it);
- if (ret >= 0)
+ if (ret >= 0) {
ret = comedi_device_postconfig(dev);
- if (ret < 0) {
- comedi_device_detach(dev);
+ if (ret < 0) {
+ comedi_device_detach(dev);
+ module_put(driv->module);
+ }
+ } else {
module_put(driv->module);
}
/* On success, the driver module count has been incremented. */
--

[syzbot]

Hello,

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

Reported-by: syzbot+6616bb...@syzkaller.appspotmail.com
Tested-by: syzbot+6616bb...@syzkaller.appspotmail.com

Tested on:

commit: a79a588f Merge tag 'pm-6.16-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=102bc582580000

kernel config: https://syzkaller.appspot.com/x/.config?x=5ba6cef8f153bfeb
dashboard link: https://syzkaller.appspot.com/bug?extid=6616bba359cec7a1def1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16a6f3d4580000

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

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Re: WARNING in driver_unregister (2)
Author: abb...@mev.co.uk

#syz test