Message-ID: <ZN/fVHbQA81Zk0Db@google.com>
Date:   Fri, 18 Aug 2023 14:15:00 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     syzbot <syzbot+e5600587fa9cbf8e3826@...kaller.appspotmail.com>
Cc:     chao@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [f2fs?] possible deadlock in f2fs_getxattr

#syz test: https://github.com/jaegeuk/f2fs.git g-dev-test

On 07/06, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a452483508d7 Merge tag 's390-6.5-2' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=161917a0a80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=15873d91ff37a949
> dashboard link: https://syzkaller.appspot.com/bug?extid=e5600587fa9cbf8e3826
> compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/5a4997524374/disk-a4524835.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a0d32791e67c/vmlinux-a4524835.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/ff545ba23349/bzImage-a4524835.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e5600587fa9cbf8e3826@...kaller.appspotmail.com
> 
> F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
> F2FS-fs (loop0): Found nat_bits in checkpoint
> F2FS-fs (loop0): Try to recover 1th superblock, ret: 0
> F2FS-fs (loop0): Mounted with checkpoint version = 48b305e5
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.4.0-syzkaller-12155-ga452483508d7 #0 Not tainted
> ------------------------------------------------------
> syz-executor.0/5180 is trying to acquire lock:
> ffff88803c1b90a0 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
> ffff88803c1b90a0 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_getxattr+0xb8/0x1460 fs/f2fs/xattr.c:532
> 
> but task is already holding lock:
> ffff88803c0196d8 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
> ffff88803c0196d8 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_do_tmpfile+0x25/0x170 fs/f2fs/dir.c:838
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (&fi->i_sem){+.+.}-{3:3}:
>        down_write+0x3a/0x50 kernel/locking/rwsem.c:1573
>        f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
>        f2fs_add_inline_entry+0x3a8/0x760 fs/f2fs/inline.c:644
>        f2fs_add_dentry+0xba/0x1e0 fs/f2fs/dir.c:784
>        f2fs_do_add_link+0x21e/0x340 fs/f2fs/dir.c:827
>        f2fs_add_link fs/f2fs/f2fs.h:3554 [inline]
>        f2fs_create+0x32c/0x530 fs/f2fs/namei.c:377
>        lookup_open fs/namei.c:3492 [inline]
>        open_last_lookups fs/namei.c:3560 [inline]
>        path_openat+0x13e7/0x3180 fs/namei.c:3790
>        do_filp_open+0x234/0x490 fs/namei.c:3820
>        do_sys_openat2+0x13e/0x1d0 fs/open.c:1407
>        do_sys_open fs/open.c:1422 [inline]
>        __do_sys_open fs/open.c:1430 [inline]
>        __se_sys_open fs/open.c:1426 [inline]
>        __x64_sys_open+0x225/0x270 fs/open.c:1426
>        do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>        do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>        entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> -> #0 (&fi->i_xattr_sem){.+.+}-{3:3}:
>        check_prev_add kernel/locking/lockdep.c:3142 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3261 [inline]
>        validate_chain kernel/locking/lockdep.c:3876 [inline]
>        __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5144
>        lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761
>        down_read+0x47/0x2f0 kernel/locking/rwsem.c:1520
>        f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
>        f2fs_getxattr+0xb8/0x1460 fs/f2fs/xattr.c:532
>        __f2fs_get_acl+0x52/0x8e0 fs/f2fs/acl.c:179
>        f2fs_acl_create fs/f2fs/acl.c:377 [inline]
>        f2fs_init_acl+0xd7/0x9a0 fs/f2fs/acl.c:420
>        f2fs_init_inode_metadata+0x824/0x1190 fs/f2fs/dir.c:558
>        f2fs_do_tmpfile+0x34/0x170 fs/f2fs/dir.c:839
>        __f2fs_tmpfile+0x1f9/0x380 fs/f2fs/namei.c:884
>        f2fs_ioc_start_atomic_write+0x4a3/0x9e0 fs/f2fs/file.c:2099
>        __f2fs_ioctl+0x1b5c/0xb770
>        vfs_ioctl fs/ioctl.c:51 [inline]
>        __do_sys_ioctl fs/ioctl.c:870 [inline]
>        __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856
>        do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>        do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>        entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> other info that might help us debug this:
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(&fi->i_sem);
>                                lock(&fi->i_xattr_sem);
>                                lock(&fi->i_sem);
>   rlock(&fi->i_xattr_sem);
> 
>  *** DEADLOCK ***
> 
> 5 locks held by syz-executor.0/5180:
>  #0: ffff888078fb2410 (sb_writers#16){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:447
>  #1: ffff88803c018a28 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:771 [inline]
>  #1: ffff88803c018a28 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: f2fs_ioc_start_atomic_write+0x1b2/0x9e0 fs/f2fs/file.c:2060
>  #2: ffff88803c019008 (&fi->i_gc_rwsem[WRITE]){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
>  #2: ffff88803c019008 (&fi->i_gc_rwsem[WRITE]){+.+.}-{3:3}, at: f2fs_ioc_start_atomic_write+0x276/0x9e0 fs/f2fs/file.c:2074
>  #3: ffff88802b7e03b0 (&sbi->cp_rwsem){.+.+}-{3:3}, at: f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
>  #3: ffff88802b7e03b0 (&sbi->cp_rwsem){.+.+}-{3:3}, at: f2fs_lock_op fs/f2fs/f2fs.h:2151 [inline]
>  #3: ffff88802b7e03b0 (&sbi->cp_rwsem){.+.+}-{3:3}, at: __f2fs_tmpfile+0x1ce/0x380 fs/f2fs/namei.c:879
>  #4: ffff88803c0196d8 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
>  #4: ffff88803c0196d8 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_do_tmpfile+0x25/0x170 fs/f2fs/dir.c:838
> 
> stack backtrace:
> CPU: 1 PID: 5180 Comm: syz-executor.0 Not tainted 6.4.0-syzkaller-12155-ga452483508d7 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
>  check_noncircular+0x375/0x4a0 kernel/locking/lockdep.c:2195
>  check_prev_add kernel/locking/lockdep.c:3142 [inline]
>  check_prevs_add kernel/locking/lockdep.c:3261 [inline]
>  validate_chain kernel/locking/lockdep.c:3876 [inline]
>  __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5144
>  lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761
>  down_read+0x47/0x2f0 kernel/locking/rwsem.c:1520
>  f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
>  f2fs_getxattr+0xb8/0x1460 fs/f2fs/xattr.c:532
>  __f2fs_get_acl+0x52/0x8e0 fs/f2fs/acl.c:179
>  f2fs_acl_create fs/f2fs/acl.c:377 [inline]
>  f2fs_init_acl+0xd7/0x9a0 fs/f2fs/acl.c:420
>  f2fs_init_inode_metadata+0x824/0x1190 fs/f2fs/dir.c:558
>  f2fs_do_tmpfile+0x34/0x170 fs/f2fs/dir.c:839
>  __f2fs_tmpfile+0x1f9/0x380 fs/f2fs/namei.c:884
>  f2fs_ioc_start_atomic_write+0x4a3/0x9e0 fs/f2fs/file.c:2099
>  __f2fs_ioctl+0x1b5c/0xb770
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fc9e168c389
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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:00007fc9e2476168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fc9e17abf80 RCX: 00007fc9e168c389
> RDX: 0000000000000000 RSI: 000000000000f501 RDI: 0000000000000005
> RBP: 00007fc9e16d7493 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fffcc104f8f R14: 00007fc9e2476300 R15: 0000000000022000
>  </TASK>
> 
> 
> ---
> 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 syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want to change bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup

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