[v6.1] possible deadlock in iterate_dir

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Jul 14, 2023, 1:21:47 AM7/14/23
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Hello,

syzbot found the following issue on:

HEAD commit: 61fd484b2cf6 Linux 6.1.38
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13b215eaa80000
kernel config: https://syzkaller.appspot.com/x/.config?x=3b4be05fdc3de90a
dashboard link: https://syzkaller.appspot.com/bug?extid=fa6c8166fd705febe592
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/710437ee8127/disk-61fd484b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a61ff183628e/vmlinux-61fd484b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/522fb55f8194/Image-61fd484b.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fa6c81...@syzkaller.appspotmail.com

REISERFS warning (device loop2): vs-13060 reiserfs_update_sd_size: stat data of object [1 2 0x0 SD] (nlink == 4) not found (pos 2)
REISERFS (device loop2): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.1.38-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/14079 is trying to acquire lock:
ffff0000d8aba090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27

but task is already holding lock:
ffff000110c20460 (sb_writers#21){.+.+}-{0:0}, at: file_accessed include/linux/fs.h:2535 [inline]
ffff000110c20460 (sb_writers#21){.+.+}-{0:0}, at: iterate_dir+0x400/0x4e4 fs/readdir.c:70

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sb_writers#21){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1832 [inline]
sb_start_write+0x7c/0x308 include/linux/fs.h:1907
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:581

-> #0 (&sbi->lock){+.+.}-{3:3}:
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+0x26c/0x7cc kernel/locking/lockdep.c:5669
__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_dirty_inode+0xe4/0x204 fs/reiserfs/super.c:704
__mark_inode_dirty+0x2f8/0x1354 fs/fs-writeback.c:2411
generic_update_time fs/inode.c:1859 [inline]
inode_update_time fs/inode.c:1872 [inline]
touch_atime+0x5f0/0x8ec fs/inode.c:1944
file_accessed include/linux/fs.h:2535 [inline]
iterate_dir+0x400/0x4e4 fs/readdir.c:70
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x1c4/0x4a0 fs/readdir.c:354
__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:581

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sb_writers#21);
lock(&sbi->lock);
lock(sb_writers#21);
lock(&sbi->lock);

*** DEADLOCK ***

3 locks held by syz-executor.2/14079:
#0: ffff00010de614e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xd8/0x104 fs/file.c:1047
#1: ffff0000e2584520 (&type->i_mutex_dir_key#13){++++}-{3:3}, at: iterate_dir+0x108/0x4e4 fs/readdir.c:55
#2: ffff000110c20460 (sb_writers#21){.+.+}-{0:0}, at: file_accessed include/linux/fs.h:2535 [inline]
#2: ffff000110c20460 (sb_writers#21){.+.+}-{0:0}, at: iterate_dir+0x400/0x4e4 fs/readdir.c:70

stack backtrace:
CPU: 1 PID: 14079 Comm: syz-executor.2 Not tainted 6.1.38-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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: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+0x26c/0x7cc kernel/locking/lockdep.c:5669
__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_dirty_inode+0xe4/0x204 fs/reiserfs/super.c:704
__mark_inode_dirty+0x2f8/0x1354 fs/fs-writeback.c:2411
generic_update_time fs/inode.c:1859 [inline]
inode_update_time fs/inode.c:1872 [inline]
touch_atime+0x5f0/0x8ec fs/inode.c:1944
file_accessed include/linux/fs.h:2535 [inline]
iterate_dir+0x400/0x4e4 fs/readdir.c:70
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x1c4/0x4a0 fs/readdir.c:354
__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:581
REISERFS warning (device loop2): vs-13060 reiserfs_update_sd_size: stat data of object [1 2 0x0 SD] (nlink == 4) not found (pos 2)


---
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syzbot

unread,
Oct 27, 2023, 4:39:13 PM10/27/23
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.
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