possible deadlock in ovl_maybe_copy_up

From: syzbot
Date: Mon Nov 23 2020 - 05:06:00 EST

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Hello,

syzbot found the following issue on:

HEAD commit: a349e4c6 Merge tag 'xfs-5.10-fixes-7' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11813299500000
kernel config: https://syzkaller.appspot.com/x/.config?x=a521022462477aea
dashboard link: https://syzkaller.appspot.com/bug?extid=c18f2f6a7b08c51e3025
compiler: gcc (GCC) 10.1.0-syz 20200507

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+c18f2f6a7b08c51e3025@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.10.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/12280 is trying to acquire lock:
ffff8881480c8460 (sb_writers#4){.+.+}-{0:0}, at: ovl_maybe_copy_up+0x11f/0x190 fs/overlayfs/copy_up.c:990

but task is already holding lock:
ffff888011c1a740 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x363/0x1760 security/integrity/ima/ima_main.c:253

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&iint->mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:956 [inline]
__mutex_lock+0x134/0x10e0 kernel/locking/mutex.c:1103
process_measurement+0x363/0x1760 security/integrity/ima/ima_main.c:253
ima_file_check+0xb9/0x100 security/integrity/ima/ima_main.c:498
do_open fs/namei.c:3254 [inline]
path_openat+0x154d/0x2730 fs/namei.c:3369
do_filp_open+0x17e/0x3c0 fs/namei.c:3396
do_sys_openat2+0x16d/0x420 fs/open.c:1168
do_sys_open fs/open.c:1184 [inline]
__do_sys_openat fs/open.c:1200 [inline]
__se_sys_openat fs/open.c:1195 [inline]
__x64_sys_openat+0x13f/0x1f0 fs/open.c:1195
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #0 (sb_writers#4){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:2866 [inline]
check_prevs_add kernel/locking/lockdep.c:2991 [inline]
validate_chain kernel/locking/lockdep.c:3606 [inline]
__lock_acquire+0x2ca6/0x5c00 kernel/locking/lockdep.c:4830
lock_acquire kernel/locking/lockdep.c:5435 [inline]
lock_acquire+0x2a3/0x8c0 kernel/locking/lockdep.c:5400
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1594 [inline]
sb_start_write include/linux/fs.h:1664 [inline]
mnt_want_write+0x69/0x3d0 fs/namespace.c:354
ovl_maybe_copy_up+0x11f/0x190 fs/overlayfs/copy_up.c:990
ovl_open+0xba/0x270 fs/overlayfs/file.c:154
do_dentry_open+0x4b9/0x11b0 fs/open.c:817
vfs_open fs/open.c:931 [inline]
dentry_open+0x132/0x1d0 fs/open.c:947
ima_calc_file_hash+0x32b/0x5a0 security/integrity/ima/ima_crypto.c:557
ima_collect_measurement+0x4ca/0x570 security/integrity/ima/ima_api.c:250
process_measurement+0xca6/0x1760 security/integrity/ima/ima_main.c:330
ima_file_check+0xb9/0x100 security/integrity/ima/ima_main.c:498
do_open fs/namei.c:3254 [inline]
path_openat+0x154d/0x2730 fs/namei.c:3369
do_filp_open+0x17e/0x3c0 fs/namei.c:3396
do_sys_openat2+0x16d/0x420 fs/open.c:1168
do_sys_open fs/open.c:1184 [inline]
__do_sys_open fs/open.c:1192 [inline]
__se_sys_open fs/open.c:1188 [inline]
__x64_sys_open+0x119/0x1c0 fs/open.c:1188
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&iint->mutex);
lock(sb_writers#4);
lock(&iint->mutex);
lock(sb_writers#4);

*** DEADLOCK ***

1 lock held by syz-executor.4/12280:
#0: ffff888011c1a740 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x363/0x1760 security/integrity/ima/ima_main.c:253

stack backtrace:
CPU: 0 PID: 12280 Comm: syz-executor.4 Not tainted 5.10.0-rc4-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+0x107/0x163 lib/dump_stack.c:118
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2115
check_prev_add kernel/locking/lockdep.c:2866 [inline]
check_prevs_add kernel/locking/lockdep.c:2991 [inline]
validate_chain kernel/locking/lockdep.c:3606 [inline]
__lock_acquire+0x2ca6/0x5c00 kernel/locking/lockdep.c:4830
lock_acquire kernel/locking/lockdep.c:5435 [inline]
lock_acquire+0x2a3/0x8c0 kernel/locking/lockdep.c:5400
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1594 [inline]
sb_start_write include/linux/fs.h:1664 [inline]
mnt_want_write+0x69/0x3d0 fs/namespace.c:354
ovl_maybe_copy_up+0x11f/0x190 fs/overlayfs/copy_up.c:990
ovl_open+0xba/0x270 fs/overlayfs/file.c:154
do_dentry_open+0x4b9/0x11b0 fs/open.c:817
vfs_open fs/open.c:931 [inline]
dentry_open+0x132/0x1d0 fs/open.c:947
ima_calc_file_hash+0x32b/0x5a0 security/integrity/ima/ima_crypto.c:557
ima_collect_measurement+0x4ca/0x570 security/integrity/ima/ima_api.c:250
process_measurement+0xca6/0x1760 security/integrity/ima/ima_main.c:330
ima_file_check+0xb9/0x100 security/integrity/ima/ima_main.c:498
do_open fs/namei.c:3254 [inline]
path_openat+0x154d/0x2730 fs/namei.c:3369
do_filp_open+0x17e/0x3c0 fs/namei.c:3396
do_sys_openat2+0x16d/0x420 fs/open.c:1168
do_sys_open fs/open.c:1184 [inline]
__do_sys_open fs/open.c:1192 [inline]
__se_sys_open fs/open.c:1188 [inline]
__x64_sys_open+0x119/0x1c0 fs/open.c:1188
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45deb9
Code: 0d b4 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fccb9104c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00000000000221c0 RCX: 000000000045deb9
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000020000040
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffc3967e2bf R14: 00007fccb91059c0 R15: 000000000118bf2c
overlayfs: upperdir is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.

---
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Next message: Vincent Guittot: "Re: [RFC] Documentation/scheduler/schedutil.txt"
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