syzbot


WARNING: suspicious RCU usage in kernfs_iop_permission

Status: fixed on 2021/03/10 01:48
Subsystems: kernfs
[Documentation on labels]
Reported-by: syzbot+0e507d08417ca2d565bf@syzkaller.appspotmail.com
Fix commit: b854cc659dcb ovl: avoid deadlock on directory ioctl
First crash: 1232d, last: 1232d
Cause bisection: introduced by (bisect log) :
commit 89bdfaf93d9157499c3a0d61f489df66f2dead7f
Author: Miklos Szeredi <mszeredi@redhat.com>
Date: Mon Dec 14 14:26:14 2020 +0000

  ovl: make ioctl() safe

Crash: possible deadlock in ovl_dir_real_file (log)
Repro: C syz .config
  
Discussions (1)
Title Replies (including bot) Last reply
WARNING: suspicious RCU usage in kernfs_iop_permission 1 (2) 2021/02/01 10:06

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.11.0-rc5-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:7932 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/1.

stack backtrace:
CPU: 0 PID: 1 Comm: systemd Not tainted 5.11.0-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+0x137/0x1be lib/dump_stack.c:120
 ___might_sleep+0xb4/0x530 kernel/sched/core.c:7932
 __mutex_lock_common+0x4e/0x2f00 kernel/locking/mutex.c:935
 __mutex_lock kernel/locking/mutex.c:1103 [inline]
 mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118
 kernfs_iop_permission+0x66/0x2f0 fs/kernfs/inode.c:284
 do_inode_permission fs/namei.c:398 [inline]
 inode_permission+0x234/0x4a0 fs/namei.c:463
 may_lookup fs/namei.c:1575 [inline]
 link_path_walk+0x226/0xc10 fs/namei.c:2128
 path_openat+0x1f5/0x37a0 fs/namei.c:3367
 do_filp_open+0x191/0x3a0 fs/namei.c:3398
 do_sys_openat2+0xba/0x380 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0x1af/0x1e0 fs/open.c:1192
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fdaf5f1370d
Code: 30 2c 00 00 75 10 b8 02 00 00 00 0f 05 48 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 fe 9d 01 00 48 89 04 24 b8 02 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 47 9e 01 00 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffedccb56f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 000055b998e80590 RCX: 00007fdaf5f1370d
RDX: 00000000000001b6 RSI: 0000000000080000 RDI: 00007ffedccb57d0
RBP: 0000000000000008 R08: 0000000000000008 R09: 0000000000000001
R10: 0000000000080000 R11: 0000000000000293 R12: 00007fdaf764d7b4
R13: 0000000000000001 R14: 000055b998d5ad60 R15: 00007ffedccb57d0

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2021/02/01 04:16 upstream 6642d600b541 fc9fd31e .config console log report syz C ci-upstream-kasan-gce-smack-root WARNING: suspicious RCU usage in kernfs_iop_permission
* Struck through repros no longer work on HEAD.