[syzbot] [fs?] possible deadlock in sys_quotactl_fd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    76f598ba7d8e Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13965b21c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5666fa6aca264e42
dashboard link: https://syzkaller.appspot.com/bug?extid=aacb82fca60873422114
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/1f01c9748997/disk-76f598ba.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b3afb4fc86b9/vmlinux-76f598ba.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8908040d7a31/bzImage-76f598ba.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aacb82fca60873422114@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.3.0-rc5-syzkaller-00022-g76f598ba7d8e #0 Not tainted
------------------------------------------------------
syz-executor.0/17940 is trying to acquire lock:
ffff88802a89e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
ffff88802a89e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972

but task is already holding lock:
ffff88802a89e460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#4){.+.+}-{0:0}:
       lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1477 [inline]
       sb_start_write include/linux/fs.h:1552 [inline]
       write_mmp_block+0xe5/0x930 fs/ext4/mmp.c:50
       ext4_multi_mount_protect+0x364/0x990 fs/ext4/mmp.c:343
       __ext4_remount fs/ext4/super.c:6543 [inline]
       ext4_reconfigure+0x29a8/0x3280 fs/ext4/super.c:6642
       reconfigure_super+0x3c9/0x7c0 fs/super.c:956
       vfs_fsconfig_locked fs/fsopen.c:254 [inline]
       __do_sys_fsconfig fs/fsopen.c:439 [inline]
       __se_sys_fsconfig+0xa29/0xf70 fs/fsopen.c:314
       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 (&type->s_umount_key#31){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
       lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
       down_read+0x3d/0x50 kernel/locking/rwsem.c:1520
       __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
       __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972
       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(sb_writers#4);
                               lock(&type->s_umount_key#31);
                               lock(sb_writers#4);
  lock(&type->s_umount_key#31);

 *** DEADLOCK ***

1 lock held by syz-executor.0/17940:
 #0: ffff88802a89e460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394

stack backtrace:
CPU: 0 PID: 17940 Comm: syz-executor.0 Not tainted 6.3.0-rc5-syzkaller-00022-g76f598ba7d8e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2fe/0x3b0 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
 lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669
 down_read+0x3d/0x50 kernel/locking/rwsem.c:1520
 __do_sys_quotactl_fd fs/quota/quota.c:999 [inline]
 __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972
 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: 0033:0x7f3c2aa8c169
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:00007f3c2b826168 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb
RAX: ffffffffffffffda RBX: 00007f3c2ababf80 RCX: 00007f3c2aa8c169
RDX: ffffffffffffffff RSI: ffffffff80000601 RDI: 0000000000000003
RBP: 00007f3c2aae7ca1 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000200024c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd71f38adf R14: 00007f3c2b826300 R15: 0000000000022000
 </TASK>


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