possible deadlock in acct_pin_kill

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syzbot

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Apr 17, 2019, 4:56:06 PM4/17/19

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Hello,

syzbot found the following crash on:

HEAD commit: 4b0e041c Linux 4.19.35
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16ddb58f200000
kernel config: https://syzkaller.appspot.com/x/.config?x=bb1bcac868b1655e
dashboard link: https://syzkaller.appspot.com/bug?extid=901f82aaeb7e6a6caf27
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+901f82...@syzkaller.appspotmail.com

overlayfs: unrecognized mount option "w&W� ݈QS]:��orkdir=./file1" or
missing value
======================================================
WARNING: possible circular locking dependency detected
4.19.35 #3 Not tainted
------------------------------------------------------
syz-executor.0/13760 is trying to acquire lock:
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
00000000359e4b27 (&acct->lock#2){+.+.}, at: acct_pin_kill+0x27/0x100
kernel/acct.c:173
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'

but task is already holding lock:
0000000069cd56c5 (sb_writers#4){.+.+}, at: sb_start_write
include/linux/fs.h:1569 [inline]
0000000069cd56c5 (sb_writers#4){.+.+}, at: mnt_want_write+0x3f/0xc0
fs/namespace.c:360

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#4){.+.+}:
percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36
[inline]
percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
__sb_start_write+0x20b/0x360 fs/super.c:1387
sb_start_write include/linux/fs.h:1569 [inline]
mnt_want_write+0x3f/0xc0 fs/namespace.c:360
ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24
ovl_link+0x7c/0x2d5 fs/overlayfs/dir.c:674
vfs_link+0x7a4/0xb60 fs/namei.c:4240
do_linkat+0x550/0x770 fs/namei.c:4308
__do_sys_link fs/namei.c:4337 [inline]
__se_sys_link fs/namei.c:4335 [inline]
__x64_sys_link+0x61/0x80 fs/namei.c:4335
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&ovl_i_mutex_key[depth]){+.+.}:
down_write+0x38/0x90 kernel/locking/rwsem.c:70
inode_lock include/linux/fs.h:738 [inline]
ovl_write_iter+0x148/0xc20 fs/overlayfs/file.c:231
call_write_iter include/linux/fs.h:1811 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x58e/0x820 fs/read_write.c:487
__kernel_write+0x110/0x390 fs/read_write.c:506
do_acct_process+0xd37/0x1150 kernel/acct.c:520
slow_acct_process kernel/acct.c:579 [inline]
acct_process+0x568/0x61e kernel/acct.c:605
do_exit+0x17c0/0x2fa0 kernel/exit.c:866
do_group_exit+0x135/0x370 kernel/exit.c:979
__do_sys_exit_group kernel/exit.c:990 [inline]
__se_sys_exit_group kernel/exit.c:988 [inline]
__x64_sys_exit_group+0x44/0x50 kernel/exit.c:988
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&acct->lock#2){+.+.}:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
__mutex_lock_common kernel/locking/mutex.c:925 [inline]
__mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
acct_pin_kill+0x27/0x100 kernel/acct.c:173
pin_kill+0x18f/0x860 fs/fs_pin.c:50
acct_on+0x574/0x790 kernel/acct.c:254
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct kernel/acct.c:273 [inline]
__x64_sys_acct+0xae/0x200 kernel/acct.c:273
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&acct->lock#2 --> &ovl_i_mutex_key[depth] --> sb_writers#4

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#4);
lock(&ovl_i_mutex_key[depth]);
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
lock(sb_writers#4);
lock(&acct->lock#2);

*** DEADLOCK ***

2 locks held by syz-executor.0/13760:
#0: 00000000d8f61b5f (acct_on_mutex){+.+.}, at: __do_sys_acct
kernel/acct.c:285 [inline]
#0: 00000000d8f61b5f (acct_on_mutex){+.+.}, at: __se_sys_acct
kernel/acct.c:273 [inline]
#0: 00000000d8f61b5f (acct_on_mutex){+.+.}, at: __x64_sys_acct+0xa6/0x200
kernel/acct.c:273
#1:
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
0000000069cd56c5 (sb_writers#4){.+.+}, at: sb_start_write
include/linux/fs.h:1569 [inline]
0000000069cd56c5 (sb_writers#4){.+.+}, at: mnt_want_write+0x3f/0xc0
fs/namespace.c:360

stack backtrace:
CPU: 0 PID: 13760 Comm: syz-executor.0 Not tainted 4.19.35 #3
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+0x172/0x1f0 lib/dump_stack.c:113
print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1221
check_prev_add kernel/locking/lockdep.c:1861 [inline]
check_prevs_add kernel/locking/lockdep.c:1974 [inline]
validate_chain kernel/locking/lockdep.c:2415 [inline]
__lock_acquire+0x2e6d/0x48f0 kernel/locking/lockdep.c:3411
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
__mutex_lock_common kernel/locking/mutex.c:925 [inline]
__mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
acct_pin_kill+0x27/0x100 kernel/acct.c:173
pin_kill+0x18f/0x860 fs/fs_pin.c:50
acct_on+0x574/0x790 kernel/acct.c:254
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct kernel/acct.c:273 [inline]
__x64_sys_acct+0xae/0x200 kernel/acct.c:273
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
Code: ad b8 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 b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd2f4175c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd2f41766d4
R13: 00000000004beb3f R14: 00000000004cf8d0 R15: 00000000ffffffff
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
overlayfs: missing 'lowerdir'
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
overlayfs: unrecognized mount option "low�rdir=./file1" or missing value
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
overlayfs: missing 'lowerdir'
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: './file0' not a directory
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
Process accounting resumed
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
overlayfs: './file0' not a directory
overlayfs: './file0' not a directory
Process accounting resumed
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
overlayfs: failed to resolve './file1': -2
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
overlayfs: './file0' not a directory
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: unrecognized mount option "mp " or missing value
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
Process accounting resumed
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: './file0' not a directory
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
overlayfs: unrecognized mount option "mower" or missing value
Process accounting resumed
Process accounting resumed
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: failed to resolve './file1p i�m=�': -2
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: unrecognized mount option "u" or missing value
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
overlayfs: unrecognized mount option "u" or missing value
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
overlayfs: filesystem on './file0' not supported as upperdir
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: failed to resolve '.|w� �': -2
overlayfs: './file0' not a directory
overlayfs: './file0' not a directory
Process accounting resumed
overlayfs: failed to resolve '.|w� �': -2
Process accounting resumed
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
overlayfs: failed to resolve '.Jwile0': -2
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: failed to resolve '.Jwile0': -2
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: './file0' not a directory
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
Process accounting resumed
overlayfs: unrecognized mount option "@ " or missing value
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
overlayfs: unrecognized mount option "@ " or missing value
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
overlayfs: './file0' not a directory
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
Process accounting resumed
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: failed to resolve './file1': -2
overlayfs: './file0' not a directory
kobject: 'loop2' (000000005231a067): kobject_uevent_env
Process accounting resumed
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
overlayfs: failed to resolve './file1': -2
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
Process accounting resumed
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
overlayfs: './file0' not a directory
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
overlayfs: filesystem on './file0' not supported as upperdir
Process accounting resumed
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
Process accounting resumed
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: unrecognized mount option "workdir" or missing value
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: unrecognized mount option "workdir" or missing value
Process accounting resumed
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: './file0' not a directory
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
Process accounting resumed
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
overlayfs: './file0' not a directory
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
VFS: Can't find a Minix filesystem V1 | V2 | V3 on device loop1.
Process accounting resumed
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
overlayfs: unrecognized mount option "upp�X�� ߸ e4dir=./file0" or
missing value
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
overlayfs: missing 'lowerdir'
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: unrecognized mount option "upp�X�� ߸ e4dir=./file0" or
missing value
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
overlayfs: missing 'lowerdir'
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: unrecognized mount option "upperdir)./file0" or missing value
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
overlayfs: unrecognized mount option "upperdir)./file0" or missing value
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
overlayfs: './file0' not a directory
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
Process accounting resumed
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
overlayfs: './file0' not a directory
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
Process accounting resumed
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
overlayfs: './file0' not a directory
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
Process accounting resumed
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop2' (000000005231a067): kobject_uevent_env
kobject: 'loop2' (000000005231a067): fill_kobj_path: path
= '/devices/virtual/block/loop2'
overlayfs: unrecognized mount option "lowe��\ ��i?81" or missing value
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
overlayfs: unrecognized mount option "lowe��\ ��i?81" or missing value
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop4' (00000000607248e4): kobject_uevent_env
kobject: 'loop4' (00000000607248e4): fill_kobj_path: path
= '/devices/virtual/block/loop4'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
kobject: 'loop0' (0000000098b295a2): kobject_uevent_env
kobject: 'loop0' (0000000098b295a2): fill_kobj_path: path
= '/devices/virtual/block/loop0'
kobject: 'loop3' (00000000c27ed7d3): kobject_uevent_env
kobject: 'loop3' (00000000c27ed7d3): fill_kobj_path: path
= '/devices/virtual/block/loop3'
kobject: 'loop1' (00000000964003c0): kobject_uevent_env
kobject: 'loop1' (00000000964003c0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
overlayfs: './file0' not a directory
Process accounting resumed
Process accounting resumed

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

syzbot

unread,

Apr 17, 2019, 11:05:05 PM4/17/19

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following crash on:

HEAD commit: 4b0e041c Linux 4.19.35
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1594366b200000

kernel config: https://syzkaller.appspot.com/x/.config?x=bb1bcac868b1655e
dashboard link: https://syzkaller.appspot.com/bug?extid=901f82aaeb7e6a6caf27
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14b32dfd200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+901f82...@syzkaller.appspotmail.com

Process accounting resumed
overlayfs: failed to resolve './file1': -2
Process accounting resumed
overlayfs: failed to resolve './file1': -2

======================================================
WARNING: possible circular locking dependency detected
4.19.35 #3 Not tainted
------------------------------------------------------

syz-executor.0/7855 is trying to acquire lock:
0000000024ea9816 (&acct->lock#2){+.+.}, at: acct_pin_kill+0x27/0x100
kernel/acct.c:173

but task is already holding lock:

000000002cf51de9 (sb_writers#4){.+.+}, at: sb_start_write
include/linux/fs.h:1569 [inline]
000000002cf51de9 (sb_writers#4){.+.+}, at: mnt_want_write+0x3f/0xc0

get_signal+0x399/0x1d50 kernel/signal.c:2572
do_signal+0x95/0x1950 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293

entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&acct->lock#2){+.+.}:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
__mutex_lock_common kernel/locking/mutex.c:925 [inline]
__mutex_lock+0xf7/0x1300 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
acct_pin_kill+0x27/0x100 kernel/acct.c:173
pin_kill+0x18f/0x860 fs/fs_pin.c:50
acct_on+0x574/0x790 kernel/acct.c:254
__do_sys_acct kernel/acct.c:286 [inline]
__se_sys_acct kernel/acct.c:273 [inline]
__x64_sys_acct+0xae/0x200 kernel/acct.c:273
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&acct->lock#2 --> &ovl_i_mutex_key[depth] --> sb_writers#4

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#4);
lock(&ovl_i_mutex_key[depth]);

lock(sb_writers#4);
lock(&acct->lock#2);

*** DEADLOCK ***

2 locks held by syz-executor.0/7855:
#0: 00000000f7695be1 (acct_on_mutex){+.+.}, at: __do_sys_acct
kernel/acct.c:285 [inline]
#0: 00000000f7695be1 (acct_on_mutex){+.+.}, at: __se_sys_acct
kernel/acct.c:273 [inline]
#0: 00000000f7695be1 (acct_on_mutex){+.+.}, at: __x64_sys_acct+0xa6/0x200
kernel/acct.c:273
#1: 000000002cf51de9 (sb_writers#4){.+.+}, at: sb_start_write
include/linux/fs.h:1569 [inline]
#1: 000000002cf51de9 (sb_writers#4){.+.+}, at: mnt_want_write+0x3f/0xc0
fs/namespace.c:360

stack backtrace:
CPU: 1 PID: 7855 Comm: syz-executor.0 Not tainted 4.19.35 #3

RSP: 002b:00007fdc400f3c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3

RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200000c0

RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fdc400f46d4

R13: 00000000004beb3f R14: 00000000004cf8d0 R15: 00000000ffffffff

Process accounting resumed
kobject: 'loop0' (0000000005f778dc): kobject_uevent_env
kobject: 'loop0' (0000000005f778dc): fill_kobj_path: path
= '/devices/virtual/block/loop0'
overlayfs: failed to resolve './file1': -2
Process accounting resumed
kobject: 'loop0' (0000000005f778dc): kobject_uevent_env