[v5.15] possible deadlock in chmod_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ddcaf4999061 Linux 5.15.147
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11220ff5e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=ab92786ed9f7c373
dashboard link: https://syzkaller.appspot.com/bug?extid=9e4ec1ced4ce15bea703
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f538e3b5b6b/disk-ddcaf499.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aff958e6c838/vmlinux-ddcaf499.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b812c40b66fa/Image-ddcaf499.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9e4ec1...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.147-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/4260 is trying to acquire lock:
ffff0001147c02e0 (&type->i_mutex_dir_key#8){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
ffff0001147c02e0 (&type->i_mutex_dir_key#8){+.+.}-{3:3}, at: chmod_common+0x17c/0x418 fs/open.c:576

but task is already holding lock:
ffff0000c1c64460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:377

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#13){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1785 [inline]
sb_start_write+0xf0/0x3ac include/linux/fs.h:1855
mnt_want_write_file+0x64/0x1e8 fs/namespace.c:421
reiserfs_ioctl+0x188/0x4b8 fs/reiserfs/ioctl.c:103
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&sbi->lock){+.+.}-{3:3}:
__mutex_lock_common+0x194/0x2154 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0xa4/0xf8 kernel/locking/mutex.c:743
reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
reiserfs_lookup+0x130/0x3c4 fs/reiserfs/namei.c:364
__lookup_slow+0x250/0x388 fs/namei.c:1663
lookup_one_len+0x178/0x28c fs/namei.c:2718
reiserfs_lookup_privroot+0x8c/0x204 fs/reiserfs/xattr.c:980
reiserfs_fill_super+0x1aec/0x1e8c fs/reiserfs/super.c:2178
mount_bdev+0x274/0x370 fs/super.c:1387
get_super_block+0x44/0x58 fs/reiserfs/super.c:2608
legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
vfs_get_tree+0x90/0x274 fs/super.c:1517
do_new_mount+0x25c/0x8c4 fs/namespace.c:2994
path_mount+0x594/0x101c fs/namespace.c:3324
do_mount fs/namespace.c:3337 [inline]
__do_sys_mount fs/namespace.c:3545 [inline]
__se_sys_mount fs/namespace.c:3522 [inline]
__arm64_sys_mount+0x510/0x5e0 fs/namespace.c:3522
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (&type->i_mutex_dir_key#8){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
down_write+0x110/0x260 kernel/locking/rwsem.c:1541
inode_lock include/linux/fs.h:787 [inline]
chmod_common+0x17c/0x418 fs/open.c:576
vfs_fchmod fs/open.c:598 [inline]
__do_sys_fchmod fs/open.c:607 [inline]
__se_sys_fchmod fs/open.c:601 [inline]
__arm64_sys_fchmod+0xe0/0x150 fs/open.c:601
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
&type->i_mutex_dir_key#8 --> &sbi->lock --> sb_writers#13

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#13);
lock(&sbi->lock);
lock(sb_writers#13);
lock(&type->i_mutex_dir_key#8);

*** DEADLOCK ***

1 lock held by syz-executor.0/4260:
#0: ffff0000c1c64460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:377

stack backtrace:
CPU: 1 PID: 4260 Comm: syz-executor.0 Not tainted 5.15.147-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call trace:
dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2011
check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
down_write+0x110/0x260 kernel/locking/rwsem.c:1541
inode_lock include/linux/fs.h:787 [inline]
chmod_common+0x17c/0x418 fs/open.c:576
vfs_fchmod fs/open.c:598 [inline]
__do_sys_fchmod fs/open.c:607 [inline]
__se_sys_fchmod fs/open.c:601 [inline]
__arm64_sys_fchmod+0xe0/0x150 fs/open.c:601
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.