possible deadlock in proc_pid_personality (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: eb575cd5 Linux 4.19.195
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15eb3c64300000
kernel config: https://syzkaller.appspot.com/x/.config?x=5506475cccaff975
dashboard link: https://syzkaller.appspot.com/bug?extid=62c5b96f51407a167d76

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+62c5b9...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
4.19.195-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/20485 is trying to acquire lock:
00000000ac602118 (&sig->cred_guard_mutex){+.+.}, at: lock_trace fs/proc/base.c:402 [inline]
00000000ac602118 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_personality+0x4a/0x170 fs/proc/base.c:2938

but task is already holding lock:
000000002214a409 (&p->lock){+.+.}, at: seq_read+0x6b/0x1160 fs/seq_file.c:161

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->lock){+.+.}:
seq_read+0x6b/0x1160 fs/seq_file.c:161
proc_reg_read+0x1bd/0x2d0 fs/proc/inode.c:231
do_loop_readv_writev fs/read_write.c:701 [inline]
do_loop_readv_writev fs/read_write.c:688 [inline]
do_iter_read+0x471/0x630 fs/read_write.c:925
vfs_readv+0xe5/0x150 fs/read_write.c:987
kernel_readv fs/splice.c:362 [inline]
default_file_splice_read+0x457/0xa00 fs/splice.c:417
do_splice_to+0x10e/0x160 fs/splice.c:881
splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
do_splice_direct+0x1a7/0x270 fs/splice.c:1068
do_sendfile+0x550/0xc30 fs/read_write.c:1447
__do_sys_sendfile64 fs/read_write.c:1508 [inline]
__se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (sb_writers#3){.+.+}:
sb_start_write include/linux/fs.h:1579 [inline]
mnt_want_write+0x3a/0xb0 fs/namespace.c:360
ovl_create_object+0x96/0x290 fs/overlayfs/dir.c:600
lookup_open+0x893/0x1a20 fs/namei.c:3235
do_last fs/namei.c:3327 [inline]
path_openat+0x1094/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
inode_lock_shared include/linux/fs.h:758 [inline]
do_last fs/namei.c:3326 [inline]
path_openat+0x17ec/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_open_execat+0x11d/0x5b0 fs/exec.c:853
__do_execve_file+0x1a8b/0x2360 fs/exec.c:1770
do_execveat_common fs/exec.c:1879 [inline]
do_execve+0x35/0x50 fs/exec.c:1896
__do_sys_execve fs/exec.c:1977 [inline]
__se_sys_execve fs/exec.c:1972 [inline]
__x64_sys_execve+0x7c/0xa0 fs/exec.c:1972
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&sig->cred_guard_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:938 [inline]
__mutex_lock+0xd7/0x1200 kernel/locking/mutex.c:1083
lock_trace fs/proc/base.c:402 [inline]
proc_pid_personality+0x4a/0x170 fs/proc/base.c:2938
proc_single_show+0xeb/0x170 fs/proc/base.c:755
seq_read+0x4be/0x1160 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:701 [inline]
do_loop_readv_writev fs/read_write.c:688 [inline]
do_iter_read+0x471/0x630 fs/read_write.c:925
vfs_readv+0xe5/0x150 fs/read_write.c:987
kernel_readv fs/splice.c:362 [inline]
default_file_splice_read+0x457/0xa00 fs/splice.c:417
do_splice_to+0x10e/0x160 fs/splice.c:881
splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
do_splice_direct+0x1a7/0x270 fs/splice.c:1068
do_sendfile+0x550/0xc30 fs/read_write.c:1447
__do_sys_sendfile64 fs/read_write.c:1508 [inline]
__se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
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.3/20485:
#0: 000000002214a409 (&p->lock){+.+.}, at: seq_read+0x6b/0x1160 fs/seq_file.c:161

stack backtrace:
CPU: 1 PID: 20485 Comm: syz-executor.3 Not tainted 4.19.195-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+0x1fc/0x2ef lib/dump_stack.c:118
print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2420 [inline]
__lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
__mutex_lock_common kernel/locking/mutex.c:938 [inline]
__mutex_lock+0xd7/0x1200 kernel/locking/mutex.c:1083
lock_trace fs/proc/base.c:402 [inline]
proc_pid_personality+0x4a/0x170 fs/proc/base.c:2938
proc_single_show+0xeb/0x170 fs/proc/base.c:755
seq_read+0x4be/0x1160 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:701 [inline]
do_loop_readv_writev fs/read_write.c:688 [inline]
do_iter_read+0x471/0x630 fs/read_write.c:925
vfs_readv+0xe5/0x150 fs/read_write.c:987
kernel_readv fs/splice.c:362 [inline]
default_file_splice_read+0x457/0xa00 fs/splice.c:417
do_splice_to+0x10e/0x160 fs/splice.c:881
splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
do_splice_direct+0x1a7/0x270 fs/splice.c:1068
do_sendfile+0x550/0xc30 fs/read_write.c:1447
__do_sys_sendfile64 fs/read_write.c:1508 [inline]
__se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
Bluetooth: hci5: command 0x0419 tx timeout
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f063be01188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000006
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000007f R11: 0000000000000246 R12: 000000000056c038
R13: 00007fff0d2df5af R14: 00007f063be01300 R15: 0000000000022000
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'.
audit: type=1800 audit(1624823389.443:889): pid=21267 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="file0" dev="sda1" ino=14430 res=0
audit: type=1800 audit(1624823389.473:890): pid=21274 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="file0" dev="sda1" ino=14430 res=0
netlink: 56 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 56 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 28 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 28 bytes leftover after parsing attributes in process `syz-executor.5'.
audit: type=1800 audit(1624823392.413:891): pid=21642 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="file0" dev="sda1" ino=14511 res=0
audit: type=1800 audit(1624823392.453:892): pid=21642 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="syz-executor.5" name="file0" dev="sda1" ino=14511 res=0
batman_adv: batadv0: Interface deactivated: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_0
batman_adv: batadv0: Interface deactivated: batadv_slave_1
batman_adv: batadv0: Removing interface: batadv_slave_1
device bridge_slave_1 left promiscuous mode
bridge0: port 2(bridge_slave_1) entered disabled state
device bridge_slave_0 left promiscuous mode
bridge0: port 1(bridge_slave_0) entered disabled state
device veth1_macvtap left promiscuous mode
device veth0_macvtap left promiscuous mode
device veth1_vlan left promiscuous mode
device veth0_vlan left promiscuous mode


---
This report 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 issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.