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Date:   Sat, 02 Jul 2022 10:27:30 -0700
From:   syzbot <syzbot+b42fe626038981fb7bfa@...kaller.appspotmail.com>
To:     hdanton@...a.com, linux-fsdevel@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        miklos@...redi.hu, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk, zohar@...ux.ibm.com, zohar@...ibm.com
Subject: Re: [syzbot] possible deadlock in mnt_want_write (2)

syzbot has found a reproducer for the following issue on:

HEAD commit:    089866061428 Merge tag 'libnvdimm-fixes-5.19-rc5' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11dd91f0080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=75c9ff14e1db87c0
dashboard link: https://syzkaller.appspot.com/bug?extid=b42fe626038981fb7bfa
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=167bafc0080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11aad3e0080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b42fe626038981fb7bfa@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.19.0-rc4-syzkaller-00187-g089866061428 #0 Not tainted
------------------------------------------------------
syz-executor450/3829 is trying to acquire lock:
ffff88807e574460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393

but task is already holding lock:
ffff888074de91a0 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x7d2/0x1c10 security/integrity/ima/ima_main.c:260

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&iint->mutex){+.+.}-{3:3}:
       lock_acquire+0x1a7/0x400 kernel/locking/lockdep.c:5665
       __mutex_lock_common+0x1de/0x26c0 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
       process_measurement+0x7d2/0x1c10 security/integrity/ima/ima_main.c:260
       ima_file_check+0xe7/0x160 security/integrity/ima/ima_main.c:517
       do_open fs/namei.c:3522 [inline]
       path_openat+0x2705/0x2ec0 fs/namei.c:3653
       do_filp_open+0x277/0x4f0 fs/namei.c:3680
       do_sys_openat2+0x13b/0x500 fs/open.c:1278
       do_sys_open fs/open.c:1294 [inline]
       __do_sys_open fs/open.c:1302 [inline]
       __se_sys_open fs/open.c:1298 [inline]
       __x64_sys_open+0x221/0x270 fs/open.c:1298
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x46/0xb0

-> #0 (sb_writers#4){.+.+}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain+0x185c/0x65c0 kernel/locking/lockdep.c:3829
       __lock_acquire+0x129a/0x1f80 kernel/locking/lockdep.c:5053
       lock_acquire+0x1a7/0x400 kernel/locking/lockdep.c:5665
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1699 [inline]
       sb_start_write+0x4d/0x1a0 include/linux/fs.h:1774
       mnt_want_write+0x3b/0x80 fs/namespace.c:393
       ovl_maybe_copy_up+0x124/0x190 fs/overlayfs/copy_up.c:1078
       ovl_open+0x106/0x2a0 fs/overlayfs/file.c:152
       do_dentry_open+0x789/0x1040 fs/open.c:848
       vfs_open fs/open.c:981 [inline]
       dentry_open+0xc1/0x120 fs/open.c:997
       ima_calc_file_hash+0x157/0x1cb0 security/integrity/ima/ima_crypto.c:557
       ima_collect_measurement+0x3de/0x850 security/integrity/ima/ima_api.c:292
       process_measurement+0xf87/0x1c10 security/integrity/ima/ima_main.c:337
       ima_file_check+0xe7/0x160 security/integrity/ima/ima_main.c:517
       do_open fs/namei.c:3522 [inline]
       path_openat+0x2705/0x2ec0 fs/namei.c:3653
       do_filp_open+0x277/0x4f0 fs/namei.c:3680
       do_sys_openat2+0x13b/0x500 fs/open.c:1278
       do_sys_open fs/open.c:1294 [inline]
       __do_sys_open fs/open.c:1302 [inline]
       __se_sys_open fs/open.c:1298 [inline]
       __x64_sys_open+0x221/0x270 fs/open.c:1298
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x46/0xb0

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-executor450/3829:
 #0: ffff888074de91a0 (&iint->mutex){+.+.}-{3:3}, at: process_measurement+0x7d2/0x1c10 security/integrity/ima/ima_main.c:260

stack backtrace:
CPU: 1 PID: 3829 Comm: syz-executor450 Not tainted 5.19.0-rc4-syzkaller-00187-g089866061428 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2f7/0x3b0 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain+0x185c/0x65c0 kernel/locking/lockdep.c:3829
 __lock_acquire+0x129a/0x1f80 kernel/locking/lockdep.c:5053
 lock_acquire+0x1a7/0x400 kernel/locking/lockdep.c:5665
 percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
 __sb_start_write include/linux/fs.h:1699 [inline]
 sb_start_write+0x4d/0x1a0 include/linux/fs.h:1774
 mnt_want_write+0x3b/0x80 fs/namespace.c:393
 ovl_maybe_copy_up+0x124/0x190 fs/overlayfs/copy_up.c:1078
 ovl_open+0x106/0x2a0 fs/overlayfs/file.c:152
 do_dentry_open+0x789/0x1040 fs/open.c:848
 vfs_open fs/open.c:981 [inline]
 dentry_open+0xc1/0x120 fs/open.c:997
 ima_calc_file_hash+0x157/0x1cb0 security/integrity/ima/ima_crypto.c:557
 ima_collect_measurement+0x3de/0x850 security/integrity/ima/ima_api.c:292
 process_measurement+0xf87/0x1c10 security/integrity/ima/ima_main.c:337
 ima_file_check+0xe7/0x160 security/integrity/ima/ima_main.c:517
 do_open fs/namei.c:3522 [inline]
 path_openat+0x2705/0x2ec0 fs/namei.c:3653
 do_filp_open+0x277/0x4f0 fs/namei.c:3680
 do_sys_openat2+0x13b/0x500 fs/open.c:1278
 do_sys_open fs/open.c:1294 [inline]
 __do_sys_open fs/open.c:1302 [inline]
 __se_sys_open fs/open.c:1298 [inline]
 __x64_sys_open+0x221/0x270 fs/open.c:1298
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7faf98402749
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 16 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007faf9838e2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007faf98491270 RCX: 00007faf98402749
RDX: 0000000000000000 RSI: 000000000000000b RDI: 00000000200000c0
RBP: 00007faf98458504 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 3d7269647265776f R14: 0079616c7265766f R15: 00007faf98491278
 </TASK>

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