[v6.1] possible deadlock in chmod_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6741e066ec76 Linux 6.1.87
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1628e2fd180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5d37120947ebed5a
dashboard link: https://syzkaller.appspot.com/bug?extid=328084a42c586a5d3707
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=101da22d180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1456463b180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e09aa9dab3c8/disk-6741e066.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4176a4f5a4d5/vmlinux-6741e066.xz
kernel image: https://storage.googleapis.com/syzbot-assets/970367753980/Image-6741e066.gz.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/fe5d10131902/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/4ecca9d2ea88/mount_3.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+328084...@syzkaller.appspotmail.com

REISERFS (device loop1): Using tea hash to sort names
REISERFS (device loop1): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.1.87-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor178/4341 is trying to acquire lock:
ffff0000dfa03e80 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
ffff0000dfa03e80 (&type->i_mutex_dir_key#6){+.+.}-{3:3}, at: chmod_common+0x17c/0x418 fs/open.c:600

but task is already holding lock:
ffff0000d598a460 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:393

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sb_writers#8){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1891 [inline]
sb_start_write+0x7c/0x308 include/linux/fs.h:1966
mnt_want_write_file+0x64/0x1e8 fs/namespace.c:437
reiserfs_ioctl+0x184/0x454 fs/reiserfs/ioctl.c:103
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
__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+0x64/0x218 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #1 (&sbi->lock){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
reiserfs_lookup+0x130/0x3c4 fs/reiserfs/namei.c:364
__lookup_slow+0x250/0x374 fs/namei.c:1690
lookup_one_len+0x178/0x28c fs/namei.c:2742
reiserfs_lookup_privroot+0x8c/0x204 fs/reiserfs/xattr.c:973
reiserfs_fill_super+0x15b4/0x2028 fs/reiserfs/super.c:2192
mount_bdev+0x274/0x370 fs/super.c:1432
get_super_block+0x44/0x58 fs/reiserfs/super.c:2601
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1562
do_new_mount+0x278/0x8fc fs/namespace.c:3051
path_mount+0x590/0xe5c fs/namespace.c:3381
do_mount fs/namespace.c:3394 [inline]
__do_sys_mount fs/namespace.c:3602 [inline]
__se_sys_mount fs/namespace.c:3579 [inline]
__arm64_sys_mount+0x45c/0x594 fs/namespace.c:3579
__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+0x64/0x218 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (&type->i_mutex_dir_key#6){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049
lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662
down_write+0x5c/0x88 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:758 [inline]
chmod_common+0x17c/0x418 fs/open.c:600
vfs_fchmod fs/open.c:622 [inline]
__do_sys_fchmod fs/open.c:631 [inline]
__se_sys_fchmod fs/open.c:625 [inline]
__arm64_sys_fchmod+0xe0/0x150 fs/open.c:625
__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+0x64/0x218 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

other info that might help us debug this:

Chain exists of:
&type->i_mutex_dir_key#6 --> &sbi->lock --> sb_writers#8

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#8);
lock(&sbi->lock);
lock(sb_writers#8);
lock(&type->i_mutex_dir_key#6);

*** DEADLOCK ***

1 lock held by syz-executor178/4341:
#0: ffff0000d598a460 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:393

stack backtrace:
CPU: 1 PID: 4341 Comm: syz-executor178 Not tainted 6.1.87-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call trace:
dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
dump_stack+0x1c/0x5c lib/dump_stack.c:113
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2048
check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain kernel/locking/lockdep.c:3825 [inline]
__lock_acquire+0x3338/0x7680 kernel/locking/lockdep.c:5049
lock_acquire+0x26c/0x7cc kernel/locking/lockdep.c:5662
down_write+0x5c/0x88 kernel/locking/rwsem.c:1573
inode_lock include/linux/fs.h:758 [inline]
chmod_common+0x17c/0x418 fs/open.c:600
vfs_fchmod fs/open.c:622 [inline]
__do_sys_fchmod fs/open.c:631 [inline]
__se_sys_fchmod fs/open.c:625 [inline]
__arm64_sys_fchmod+0xe0/0x150 fs/open.c:625
__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+0x64/0x218 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585


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