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Subjectpossible deadlock in process_measurement (2)
From
Hello,

syzbot found the following crash on:

HEAD commit: 81b6b964 Merge branch 'master' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17019696e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=333b76551307b2a0
dashboard link: https://syzkaller.appspot.com/bug?extid=18a1619cceea30ed45af
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+18a1619cceea30ed45af@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.4.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/596 is trying to acquire lock:
ffff88802b0761a0 (&ovl_i_mutex_key[depth]){+.+.}, at: inode_lock
include/linux/fs.h:791 [inline]
ffff88802b0761a0 (&ovl_i_mutex_key[depth]){+.+.}, at:
process_measurement+0x6f4/0x1810 security/integrity/ima/ima_main.c:230

but task is already holding lock:
ffff8880547b07d0 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds
fs/exec.c:1409 [inline]
ffff8880547b07d0 (&sig->cred_guard_mutex){+.+.}, at:
__do_execve_file.isra.0+0x376/0x22b0 fs/exec.c:1754

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&sig->cred_guard_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1136
lock_trace+0x4a/0xe0 fs/proc/base.c:406
proc_pid_personality+0x1c/0xd0 fs/proc/base.c:2961
proc_single_show+0xfd/0x1c0 fs/proc/base.c:756
seq_read+0x4ca/0x1110 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:714 [inline]
do_loop_readv_writev fs/read_write.c:701 [inline]
do_iter_read+0x4a4/0x660 fs/read_write.c:935
vfs_readv+0xf0/0x160 fs/read_write.c:997
do_preadv+0x1c4/0x280 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+0x9a/0xf0 fs/read_write.c:1134
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&p->lock){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:959 [inline]
__mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
seq_read+0x71/0x1110 fs/seq_file.c:161
do_loop_readv_writev fs/read_write.c:714 [inline]
do_loop_readv_writev fs/read_write.c:701 [inline]
do_iter_read+0x4a4/0x660 fs/read_write.c:935
vfs_readv+0xf0/0x160 fs/read_write.c:997
kernel_readv fs/splice.c:359 [inline]
default_file_splice_read+0x482/0x980 fs/splice.c:414
do_splice_to+0x127/0x180 fs/splice.c:877
splice_direct_to_actor+0x2d2/0x970 fs/splice.c:954
do_splice_direct+0x1da/0x2a0 fs/splice.c:1063
do_sendfile+0x597/0xd00 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+0x1dd/0x220 fs/read_write.c:1511
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (sb_writers#3){.+.+}:
percpu_down_read include/linux/percpu-rwsem.h:40 [inline]
__sb_start_write+0x241/0x460 fs/super.c:1672
sb_start_write include/linux/fs.h:1650 [inline]
mnt_want_write+0x3f/0xc0 fs/namespace.c:354
ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:21
ovl_setattr+0xdd/0x8b0 fs/overlayfs/inode.c:27
notify_change+0xad7/0xfb0 fs/attr.c:337
do_truncate+0x158/0x220 fs/open.c:64
handle_truncate fs/namei.c:2998 [inline]
do_last fs/namei.c:3414 [inline]
path_openat+0x2d63/0x46d0 fs/namei.c:3525
do_filp_open+0x1a1/0x280 fs/namei.c:3555
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
ksys_open include/linux/syscalls.h:1385 [inline]
__do_sys_creat fs/open.c:1155 [inline]
__se_sys_creat fs/open.c:1153 [inline]
__x64_sys_creat+0x61/0x80 fs/open.c:1153
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&ovl_i_mutex_key[depth]){+.+.}:
check_prev_add kernel/locking/lockdep.c:2476 [inline]
check_prevs_add kernel/locking/lockdep.c:2581 [inline]
validate_chain kernel/locking/lockdep.c:2971 [inline]
__lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485
down_write+0x93/0x150 kernel/locking/rwsem.c:1534
inode_lock include/linux/fs.h:791 [inline]
process_measurement+0x6f4/0x1810
security/integrity/ima/ima_main.c:230
ima_file_check+0xc5/0x110 security/integrity/ima/ima_main.c:438
do_last fs/namei.c:3412 [inline]
path_openat+0x113d/0x46d0 fs/namei.c:3525
do_filp_open+0x1a1/0x280 fs/namei.c:3555
do_open_execat+0x137/0x690 fs/exec.c:857
__do_execve_file.isra.0+0x1702/0x22b0 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+0x8f/0xc0 fs/exec.c:1956
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
&ovl_i_mutex_key[depth] --> &p->lock --> &sig->cred_guard_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sig->cred_guard_mutex);
lock(&p->lock);
lock(&sig->cred_guard_mutex);
lock(&ovl_i_mutex_key[depth]);

*** DEADLOCK ***

1 lock held by syz-executor.2/596:
#0: ffff8880547b07d0 (&sig->cred_guard_mutex){+.+.}, at:
prepare_bprm_creds fs/exec.c:1409 [inline]
#0: ffff8880547b07d0 (&sig->cred_guard_mutex){+.+.}, at:
__do_execve_file.isra.0+0x376/0x22b0 fs/exec.c:1754

stack backtrace:
CPU: 1 PID: 596 Comm: syz-executor.2 Not tainted 5.4.0-syzkaller #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+0x197/0x210 lib/dump_stack.c:118
print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1685
check_noncircular+0x32e/0x3e0 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 kernel/locking/lockdep.c:2971 [inline]
__lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485
down_write+0x93/0x150 kernel/locking/rwsem.c:1534
inode_lock include/linux/fs.h:791 [inline]
process_measurement+0x6f4/0x1810 security/integrity/ima/ima_main.c:230
ima_file_check+0xc5/0x110 security/integrity/ima/ima_main.c:438
do_last fs/namei.c:3412 [inline]
path_openat+0x113d/0x46d0 fs/namei.c:3525
do_filp_open+0x1a1/0x280 fs/namei.c:3555
do_open_execat+0x137/0x690 fs/exec.c:857
__do_execve_file.isra.0+0x1702/0x22b0 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+0x8f/0xc0 fs/exec.c:1956
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a679
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:00007ffbf4072c78 EFLAGS: 00000246 ORIG_RAX: 000000000000003b
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a679
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffbf40736d4
R13: 00000000004c0fcd R14: 00000000004d41f0 R15: 00000000ffffffff


---
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 syzkaller@googlegroups.com.

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

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