Hello,
syzbot found the following crash on:
HEAD commit: 13b86bc4 Merge tag 'for-linus' of git://git.armlinux.org.u..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1658972f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c03e4d33fa96d51
dashboard link: https://syzkaller.appspot.com/bug?extid=f731ab05acff1872c48f
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f731ab05acff1872c48f@xxxxxxxxxxxxxxxxxxxxxxxxx
======================================================
WARNING: possible circular locking dependency detected
5.4.0-rc4+ #0 Not tainted
------------------------------------------------------
syz-executor.0/17400 is trying to acquire lock:
ffff88805f4450d0 (&sig->cred_guard_mutex){+.+.}, at: do_io_accounting
fs/proc/base.c:2773 [inline]
ffff88805f4450d0 (&sig->cred_guard_mutex){+.+.}, at:
proc_tid_io_accounting+0x156/0x200 fs/proc/base.c:2816
but task is already holding lock:
ffff88805d75a0a0 (&p->lock){+.+.}, at: seq_read+0x6e/0xd70 fs/seq_file.c:161
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (&p->lock){+.+.}:
lock_acquire+0x158/0x250 kernel/locking/lockdep.c:4487
__mutex_lock_common+0x14c/0x2e20 kernel/locking/mutex.c:956
__mutex_lock kernel/locking/mutex.c:1103 [inline]
mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118
seq_read+0x6e/0xd70 fs/seq_file.c:161
proc_reg_read+0x1e2/0x2d0 fs/proc/inode.c:223
do_loop_readv_writev fs/read_write.c:714 [inline]
do_iter_read+0x4b1/0x5b0 fs/read_write.c:935
vfs_readv+0xc2/0x120 fs/read_write.c:997
kernel_readv fs/splice.c:359 [inline]
default_file_splice_read+0x544/0x8d0 fs/splice.c:414
do_splice_to fs/splice.c:877 [inline]
splice_direct_to_actor+0x39c/0xac0 fs/splice.c:954
do_splice_direct+0x200/0x330 fs/splice.c:1063
do_sendfile+0x7e4/0xfd0 fs/read_write.c:1464
__do_sys_sendfile64 fs/read_write.c:1525 [inline]
__se_sys_sendfile64 fs/read_write.c:1511 [inline]
__x64_sys_sendfile64+0x176/0x1b0 fs/read_write.c:1511
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #2 (sb_writers#3){.+.+}:
lock_acquire+0x158/0x250 kernel/locking/lockdep.c:4487
percpu_down_read include/linux/percpu-rwsem.h:40 [inline]
__sb_start_write+0xeb/0x430 fs/super.c:1672
sb_start_write include/linux/fs.h:1650 [inline]
mnt_want_write+0x4a/0xa0 fs/namespace.c:354
ovl_want_write+0x77/0x80 fs/overlayfs/util.c:21
ovl_setattr+0x55/0x790 fs/overlayfs/inode.c:27
notify_change+0xa27/0xe70 fs/attr.c:337
chown_common+0x3a4/0x5f0 fs/open.c:652
do_fchownat+0x113/0x1c0 fs/open.c:682
__do_sys_lchown fs/open.c:707 [inline]
__se_sys_lchown fs/open.c:705 [inline]
__x64_sys_lchown+0x85/0x90 fs/open.c:705
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
lock_acquire+0x158/0x250 kernel/locking/lockdep.c:4487
down_read+0x39/0x50 kernel/locking/rwsem.c:1495
inode_lock_shared include/linux/fs.h:801 [inline]
do_last fs/namei.c:3313 [inline]
path_openat+0xa9a/0x4420 fs/namei.c:3525
do_filp_open+0x192/0x3d0 fs/namei.c:3555
do_open_execat+0xff/0x610 fs/exec.c:857
__do_execve_file+0x766/0x1cc0 fs/exec.c:1762
do_execveat_common fs/exec.c:1868 [inline]
do_execve fs/exec.c:1885 [inline]
__do_sys_execve fs/exec.c:1961 [inline]
__se_sys_execve fs/exec.c:1956 [inline]
__x64_sys_execve+0x94/0xb0 fs/exec.c:1956
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (&sig->cred_guard_mutex){+.+.}:
check_prev_add kernel/locking/lockdep.c:2476 [inline]
check_prevs_add kernel/locking/lockdep.c:2581 [inline]
validate_chain+0x161e/0x7bc0 kernel/locking/lockdep.c:2971
__lock_acquire+0xc75/0x1be0 kernel/locking/lockdep.c:3955
lock_acquire+0x158/0x250 kernel/locking/lockdep.c:4487
__mutex_lock_common+0x14c/0x2e20 kernel/locking/mutex.c:956
__mutex_lock kernel/locking/mutex.c:1103 [inline]
mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133
do_io_accounting fs/proc/base.c:2773 [inline]
proc_tid_io_accounting+0x156/0x200 fs/proc/base.c:2816
proc_single_show+0xd8/0x120 fs/proc/base.c:756
seq_read+0x4cd/0xd70 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:714 [inline]
do_iter_read+0x4b1/0x5b0 fs/read_write.c:935
vfs_readv fs/read_write.c:997 [inline]
do_preadv+0x178/0x290 fs/read_write.c:1089
__do_sys_preadv fs/read_write.c:1139 [inline]
__se_sys_preadv fs/read_write.c:1134 [inline]
__x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1134
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Chain exists of:
&sig->cred_guard_mutex --> sb_writers#3 --> &p->lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&p->lock);
lock(sb_writers#3);
lock(&p->lock);
lock(&sig->cred_guard_mutex);
*** DEADLOCK ***
1 lock held by syz-executor.0/17400:
#0: ffff88805d75a0a0 (&p->lock){+.+.}, at: seq_read+0x6e/0xd70
fs/seq_file.c:161
stack backtrace:
CPU: 1 PID: 17400 Comm: syz-executor.0 Not tainted 5.4.0-rc4+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
print_circular_bug+0xc2d/0xe60 kernel/locking/lockdep.c:1685
check_noncircular+0x206/0x3a0 kernel/locking/lockdep.c:1809
check_prev_add kernel/locking/lockdep.c:2476 [inline]
check_prevs_add kernel/locking/lockdep.c:2581 [inline]
validate_chain+0x161e/0x7bc0 kernel/locking/lockdep.c:2971
__lock_acquire+0xc75/0x1be0 kernel/locking/lockdep.c:3955
lock_acquire+0x158/0x250 kernel/locking/lockdep.c:4487
__mutex_lock_common+0x14c/0x2e20 kernel/locking/mutex.c:956
__mutex_lock kernel/locking/mutex.c:1103 [inline]
mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133
do_io_accounting fs/proc/base.c:2773 [inline]
proc_tid_io_accounting+0x156/0x200 fs/proc/base.c:2816
proc_single_show+0xd8/0x120 fs/proc/base.c:756
seq_read+0x4cd/0xd70 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:714 [inline]
do_iter_read+0x4b1/0x5b0 fs/read_write.c:935
vfs_readv fs/read_write.c:997 [inline]
do_preadv+0x178/0x290 fs/read_write.c:1089
__do_sys_preadv fs/read_write.c:1139 [inline]
__se_sys_preadv fs/read_write.c:1134 [inline]
__x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1134
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459ef9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffa4f49ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459ef9
RDX: 0000000000000001 RSI: 0000000020000980 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffa4f49f6d4
R13: 00000000004c75cc R14: 00000000004dcf78 R15: 00000000ffffffff
---
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