[syzbot] WARNING: suspicious RCU usage in dput

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1e43c377 Merge tag 'xtensa-20210329' of git://github.com/j..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d76301d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=78ef1d159159890
dashboard link: https://syzkaller.appspot.com/bug?extid=bdef67a6b28a89e6fe71

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+bdef67...@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.12.0-rc5-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8294 Illegal context switch in RCU-bh 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/4825.

stack backtrace:
CPU: 1 PID: 4825 Comm: systemd-udevd Not tainted 5.12.0-rc5-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+0x141/0x1d7 lib/dump_stack.c:120
___might_sleep+0x229/0x2c0 kernel/sched/core.c:8294
dput+0x4d/0xbc0 fs/dcache.c:870
step_into+0x2cf/0x1c80 fs/namei.c:1778
walk_component+0x171/0x6a0 fs/namei.c:1945
link_path_walk.part.0+0x712/0xc90 fs/namei.c:2266
link_path_walk fs/namei.c:2190 [inline]
path_lookupat+0xb7/0x830 fs/namei.c:2419
filename_lookup+0x19f/0x560 fs/namei.c:2453
do_readlinkat+0xcd/0x2f0 fs/stat.c:417
__do_sys_readlinkat fs/stat.c:444 [inline]
__se_sys_readlinkat fs/stat.c:441 [inline]
__x64_sys_readlinkat+0x93/0xf0 fs/stat.c:441
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fb5a7e200ba
Code: 48 8b 0d e1 bd 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 0b 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ae bd 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc9c440e38 EFLAGS: 00000202 ORIG_RAX: 000000000000010b
RAX: ffffffffffffffda RBX: 00005604089e4380 RCX: 00007fb5a7e200ba
RDX: 00005604089e4380 RSI: 00007ffc9c440ec0 RDI: 00000000ffffff9c
RBP: 0000000000000064 R08: 00007fb5a80dcbc8 R09: 0000000000000070
R10: 0000000000000063 R11: 0000000000000202 R12: 00007ffc9c440ec0
R13: 00000000ffffff9c R14: 00007ffc9c440e90 R15: 0000000000000063


---
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 syzk...@googlegroups.com.

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

[Matthew Wilcox]

#syz dup: WARNING: suspicious RCU usage in getname_flags