WARNING: suspicious RCU usage in exit_mmap

Status: fixed on 2021/11/10 00:50
Subsystems: mm
[Documentation on labels]
Fix commit: 3066820034b5 rcu: Reject RCU_LOCKDEP_WARN() false positives
First crash: 1108d, last: 1108d

Sample crash report:
WARNING: suspicious RCU usage
5.13.0-rc1-syzkaller #0 Not tainted
kernel/sched/core.c:8304 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 syz-executor.3/13043.

stack backtrace:
CPU: 0 PID: 13043 Comm: syz-executor.3 Not tainted 5.13.0-rc1-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:8304
 exit_mmap+0x355/0x590 mm/mmap.c:3220
 __mmput+0x122/0x470 kernel/fork.c:1096
 mmput+0x58/0x60 kernel/fork.c:1117
 exit_mm kernel/exit.c:502 [inline]
 do_exit+0xb0a/0x2a60 kernel/exit.c:813
 do_group_exit+0x125/0x310 kernel/exit.c:923
 get_signal+0x47f/0x2150 kernel/signal.c:2818
 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
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:57
RIP: 0033:0x4665d9
Code: Unable to access opcode bytes at RIP 0x4665af.
RSP: 002b:00007fb7e54a9188 EFLAGS: 00000246
 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 0000000000a9fb1f R14: 00007fb7e54a9300 R15: 0000000000022000

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2021/05/14 13:38 upstream 315d99318179 8bdd5343 .config console log report info ci-upstream-kasan-gce WARNING: suspicious RCU usage in exit_mmap
* Struck through repros no longer work on HEAD.