[syzbot] WARNING: suspicious RCU usage in kernfs_iop_getattr

syzbot
2021-05-03T04:33:47Z

Hello,

syzbot found the following issue on:

HEAD commit: d72cd4ad Merge tag 'scsi-misc' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123fbb85d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=53fdf14defd48c56
dashboard link: https://syzkaller.appspot.com/bug?extid=c26b2cb5301be7de9efc
compiler: Debian clang version 11.0.1-2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c26b2cb5301be7de9efc@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.12.0-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8304 Illegal context switch in RCU-sched read-side critical section!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 0
no locks held by systemd-udevd/4826.

stack backtrace:
CPU: 1 PID: 4826 Comm: systemd-udevd Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x202/0x31e lib/dump_stack.c:120
___might_sleep+0x114/0x6b0 kernel/sched/core.c:8304
__mutex_lock_common+0xce/0x2e50 kernel/locking/mutex.c:928
__mutex_lock kernel/locking/mutex.c:1096 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1111
kernfs_iop_getattr+0x89/0x310 fs/kernfs/inode.c:194
vfs_getattr fs/stat.c:134 [inline]
vfs_statx+0x1ba/0x3d0 fs/stat.c:199
vfs_fstatat fs/stat.c:217 [inline]
vfs_lstat include/linux/fs.h:3384 [inline]
__do_sys_newlstat fs/stat.c:372 [inline]
__se_sys_newlstat fs/stat.c:366 [inline]
__x64_sys_newlstat+0xd3/0x150 fs/stat.c:366
do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f41b6750335
Code: 69 db 2b 00 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 83 ff 01 48 89 f0 77 30 48 89 c7 48 89 d6 b8 06 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 03 f3 c3 90 48 8b 15 31 db 2b 00 f7 d8 64 89
RSP: 002b:00007ffe4d8d3b08 EFLAGS: 00000246
ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 00005601243f1120 RCX: 00007f41b6750335
RDX: 00007ffe4d8d3b40 RSI: 00007ffe4d8d3b40 RDI: 00005601243f0120
RBP: 00007ffe4d8d3c00 R08: 00007f41b6a0f228 R09: 0000000000001010
R10: 00007f41b6a0eb58 R11: 0000000000000246 R12: 00005601243f0120
R13: 00005601243f0134 R14: 000056012440253d R15: 0000560124402544

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.