syzbot


WARNING: suspicious RCU usage in dup_mmap

Status: fixed on 2021/11/10 00:50
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: 3066820034b5 rcu: Reject RCU_LOCKDEP_WARN() false positives
First crash: 487d, last: 487d

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.13.0-rc3-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
3 locks held by syz-executor.5/8594:
 #0: 
ffffffff8cf9e250
 (
dup_mmap_sem
){.+.+}-{0:0}
, at: dup_mmap+0xc7/0xee0 kernel/fork.c:483
 #1: 
ffff88802c20b958
 (
&mm->mmap_lock
#2
){++++}-{3:3}
, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
, at: dup_mmap+0xde/0xee0 kernel/fork.c:484
 #2: 
ffff88802c20ce58
 (
&mm->mmap_lock
/1
){+.+.}-{3:3}
, at: mmap_write_lock_nested include/linux/mmap_lock.h:78 [inline]
, at: dup_mmap+0x128/0xee0 kernel/fork.c:493

stack backtrace:
CPU: 0 PID: 8594 Comm: syz-executor.5 Not tainted 5.13.0-rc3-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
 down_write+0x77/0x170 kernel/locking/rwsem.c:1405
 i_mmap_lock_write include/linux/fs.h:494 [inline]
 dup_mmap+0x894/0xee0 kernel/fork.c:565
 dup_mm+0x8c/0x310 kernel/fork.c:1374
 copy_mm kernel/fork.c:1426 [inline]
 copy_process+0x24a3/0x57f0 kernel/fork.c:2116
 kernel_clone+0x21a/0x7d0 kernel/fork.c:2503
 __do_sys_clone kernel/fork.c:2620 [inline]
 __se_sys_clone kernel/fork.c:2604 [inline]
 __x64_sys_clone+0x236/0x2b0 kernel/fork.c:2604
 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x464bcb
Code: ed 0f 85 60 01 00 00 64 4c 8b 0c 25 10 00 00 00 45 31 c0 4d 8d 91 d0 02 00 00 31 d2 31 f6 bf 11 00 20 01 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 89 00 00 00 41 89 c5 85 c0 0f 85 90 00 00
RSP: 002b:00007ffd4d582600 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000464bcb
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000002276400
R10: 00000000022766d0 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000001 R15: 00007ffd4d5826f0

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce-smack-root 2021/05/27 23:54 upstream d7c5303fbc8a 858ea628 .config log report info WARNING: suspicious RCU usage in dup_mmap
* Struck through repros no longer work on HEAD.