[syzbot] WARNING: suspicious RCU usage in get_signal

syzbot
2021-05-06T21:34:29Z

Hello,

syzbot found the following issue on:

HEAD commit: d2b6f8a1 Merge tag 'xfs-5.13-merge-3' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123a56a5d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=65c207250bba4efe
dashboard link: https://syzkaller.appspot.com/bug?extid=37fc8b84ffa2279d636d
userspace arch: i386

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+37fc8b84ffa2279d636d@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 syz-executor.4/10430.

stack backtrace:
CPU: 0 PID: 10430 Comm: syz-executor.4 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+0x141/0x1d7 lib/dump_stack.c:120
___might_sleep+0x266/0x2c0 kernel/sched/core.c:8304
try_to_freeze_unsafe include/linux/freezer.h:57 [inline]
try_to_freeze include/linux/freezer.h:67 [inline]
get_signal+0x14a/0x2150 kernel/signal.c:2613
arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:789
handle_signal_work kernel/entry/common.c:147 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x171/0x280 kernel/entry/common.c:208
irqentry_exit_to_user_mode+0x5/0x40 kernel/entry/common.c:314
exc_page_fault+0xc6/0x180 arch/x86/mm/fault.c:1534
asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577
RIP: 0023:0x8052207
Code: 0c 50 e8 ac 5a 01 00 83 c4 10 85 c0 0f 84 b9 01 00 00 65 f0 83 2d d8 ff ff ff 01 8b 5c 24 08 e8 6f f7 00 00 8b 4c 24 0c 8b 00 <8b> 71 50 89 41 54 85 c0 75 05 83 fe ff 74 19 6b 44 24 1c 34 8b 4c
RSP: 002b:00000000f5514640 EFLAGS: 00010283
RAX: 000000000000000e RBX: 0000000000000000 RCX: 0000000000000000
RDX: 00000000080521e4 RSI: 0000000000000005 RDI: 00000000080ea51d
RBP: 000000000819afc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

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