Re: [syzbot] [ext4?] possible deadlock in ext4_multi_mount_protect

From: syzbot
Date: Sun May 07 2023 - 23:43:30 EST

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syzbot has found a reproducer for the following issue on:

HEAD commit: 14f8db1c0f9a Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1168e64c280000
kernel config: https://syzkaller.appspot.com/x/.config?x=a837a8ba7e88bb45
dashboard link: https://syzkaller.appspot.com/bug?extid=6b7df7d5506b32467149
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=159b92b8280000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14355e4c280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ad6ce516eed3/disk-14f8db1c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1f38c2cc7667/vmlinux-14f8db1c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d795115eee39/Image-14f8db1c.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/36779692cd0c/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6b7df7d5506b32467149@xxxxxxxxxxxxxxxxxxxxxxxxx

EXT4-fs (loop0): 1 truncate cleaned up
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 without journal. Quota mode: writeback.
======================================================
WARNING: possible circular locking dependency detected
6.3.0-rc7-syzkaller-g14f8db1c0f9a #0 Not tainted
------------------------------------------------------
syz-executor258/5925 is trying to acquire lock:
ffff0000dba3c460 (sb_writers#3){.+.+}-{0:0}, at: ext4_multi_mount_protect+0x2f8/0x8c8 fs/ext4/mmp.c:343

but task is already holding lock:
ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: vfs_fsconfig_locked fs/fsopen.c:253 [inline]
ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:439 [inline]
ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __se_sys_fsconfig fs/fsopen.c:314 [inline]
ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __arm64_sys_fsconfig+0xa14/0xd18 fs/fsopen.c:314

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&type->s_umount_key#29){++++}-{3:3}:
down_write+0x50/0xc0 kernel/locking/rwsem.c:1573
__do_sys_quotactl_fd fs/quota/quota.c:997 [inline]
__se_sys_quotactl_fd fs/quota/quota.c:972 [inline]
__arm64_sys_quotactl_fd+0x2fc/0x4a4 fs/quota/quota.c:972
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:193
el0_svc+0x4c/0x15c arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591

-> #0 (sb_writers#3){.+.+}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain kernel/locking/lockdep.c:3832 [inline]
__lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056
lock_acquire+0x238/0x718 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+0xe4/0xb70 fs/ext4/mmp.c:50
ext4_multi_mount_protect+0x2f8/0x8c8 fs/ext4/mmp.c:343
__ext4_remount fs/ext4/super.c:6543 [inline]
ext4_reconfigure+0x2180/0x2928 fs/ext4/super.c:6642
reconfigure_super+0x328/0x738 fs/super.c:956
vfs_fsconfig_locked fs/fsopen.c:254 [inline]
__do_sys_fsconfig fs/fsopen.c:439 [inline]
__se_sys_fsconfig fs/fsopen.c:314 [inline]
__arm64_sys_fsconfig+0xa1c/0xd18 fs/fsopen.c:314
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:193
el0_svc+0x4c/0x15c arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&type->s_umount_key#29);
lock(sb_writers#3);
lock(&type->s_umount_key#29);
lock(sb_writers#3);

*** DEADLOCK ***

2 locks held by syz-executor258/5925:
#0: ffff0000d5b8a470 (&fc->uapi_mutex){+.+.}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:437 [inline]
#0: ffff0000d5b8a470 (&fc->uapi_mutex){+.+.}-{3:3}, at: __se_sys_fsconfig fs/fsopen.c:314 [inline]
#0: ffff0000d5b8a470 (&fc->uapi_mutex){+.+.}-{3:3}, at: __arm64_sys_fsconfig+0x720/0xd18 fs/fsopen.c:314
#1: ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: vfs_fsconfig_locked fs/fsopen.c:253 [inline]
#1: ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:439 [inline]
#1: ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __se_sys_fsconfig fs/fsopen.c:314 [inline]
#1: ffff0000dba3c0e0 (&type->s_umount_key#29){++++}-{3:3}, at: __arm64_sys_fsconfig+0xa14/0xd18 fs/fsopen.c:314

stack backtrace:
CPU: 0 PID: 5925 Comm: syz-executor258 Not tainted 6.3.0-rc7-syzkaller-g14f8db1c0f9a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233
show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
dump_stack+0x1c/0x28 lib/dump_stack.c:113
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2056
check_noncircular+0x2cc/0x378 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 kernel/locking/lockdep.c:3832 [inline]
__lock_acquire+0x3338/0x764c kernel/locking/lockdep.c:5056
lock_acquire+0x238/0x718 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+0xe4/0xb70 fs/ext4/mmp.c:50
ext4_multi_mount_protect+0x2f8/0x8c8 fs/ext4/mmp.c:343
__ext4_remount fs/ext4/super.c:6543 [inline]
ext4_reconfigure+0x2180/0x2928 fs/ext4/super.c:6642
reconfigure_super+0x328/0x738 fs/super.c:956
vfs_fsconfig_locked fs/fsopen.c:254 [inline]
__do_sys_fsconfig fs/fsopen.c:439 [inline]
__se_sys_fsconfig fs/fsopen.c:314 [inline]
__arm64_sys_fsconfig+0xa1c/0xd18 fs/fsopen.c:314
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:193
el0_svc+0x4c/0x15c arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591
EXT4-fs warning (device loop0): ext4_enable_quotas:7001: Failed to enable quota tracking (type=2, err=-22, ino=15). Please run e2fsck to fix.

---
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Next message: patchwork-bot+chrome-platform: "Re: [PATCH] media: platform: cros-ec: Add aurash to the match table"
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