Re: [syzbot] [reiserfs?] possible deadlock in filename_create

Re: [syzbot] [reiserfs?] possible deadlock in filename_create

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+95cb07e3840546a4827b@syzkaller.appspotmail.com

Tested on:

commit:         1c8b86a3 Merge tag 'xsa441-6.6-tag' of git://git.kerne..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=10539c65680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b8c825e0d5f3f72
dashboard link: https://syzkaller.appspot.com/bug?extid=95cb07e3840546a4827b
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=170ed9b5680000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [reiserfs?] possible deadlock in filename_create

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    19af4a4ed414 Merge branch 'for-next/core', remote-tracking..
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=15da0ec9680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=80eedef55cd21fa4
dashboard link: https://syzkaller.appspot.com/bug?extid=95cb07e3840546a4827b
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=11957c65680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1304e6ba680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/702d996331e0/disk-19af4a4e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2a48ce0aeb32/vmlinux-19af4a4e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/332eb4a803d2/Image-19af4a4e.gz.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/a4536cf3a09f/mount_0.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/88a36e03ffba/mount_3.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+95cb07e3840546a4827b@syzkaller.appspotmail.com

REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc4-syzkaller-g19af4a4ed414 #0 Not tainted
------------------------------------------------------
syz-executor324/6098 is trying to acquire lock:
ffff0000dd376640 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:837 [inline]
ffff0000dd376640 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x204/0x468 fs/namei.c:3889

but task is already holding lock:
ffff0000d494e410 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:403

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:1571 [inline]
       sb_start_write+0x60/0x2ec include/linux/fs.h:1646
       mnt_want_write_file+0x64/0x1e8 fs/namespace.c:447
       reiserfs_ioctl+0x188/0x42c fs/reiserfs/ioctl.c:103
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl fs/ioctl.c:857 [inline]
       __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:857
       __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
       el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

-> #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+0x2c/0x38 kernel/locking/mutex.c:799
       reiserfs_write_lock+0x7c/0xe8 fs/reiserfs/lock.c:27
       reiserfs_lookup+0x128/0x45c fs/reiserfs/namei.c:364
       lookup_one_qstr_excl+0x108/0x230 fs/namei.c:1608
       filename_create+0x230/0x468 fs/namei.c:3890
       do_mkdirat+0xac/0x610 fs/namei.c:4135
       __do_sys_mkdirat fs/namei.c:4158 [inline]
       __se_sys_mkdirat fs/namei.c:4156 [inline]
       __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4156
       __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
       el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

-> #0 (
&type->i_mutex_dir_key#6/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x3370/0x75e8 kernel/locking/lockdep.c:5136
       lock_acquire+0x23c/0x71c kernel/locking/lockdep.c:5753
       down_write_nested+0x58/0xcc kernel/locking/rwsem.c:1689
       inode_lock_nested include/linux/fs.h:837 [inline]
       filename_create+0x204/0x468 fs/namei.c:3889
       do_mkdirat+0xac/0x610 fs/namei.c:4135
       __do_sys_mkdirat fs/namei.c:4158 [inline]
       __se_sys_mkdirat fs/namei.c:4156 [inline]
       __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4156
       __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
       el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
       do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
       el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678
       el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
       el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

other info that might help us debug this:

Chain exists of:
  &type->i_mutex_dir_key#6/1 --> &sbi->lock --> sb_writers#8

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_writers#8);
                               lock(&sbi->lock);
                               lock(sb_writers#8);
  lock(&type->i_mutex_dir_key#6/1);

 *** DEADLOCK ***

1 lock held by syz-executor324/6098:
 #0: ffff0000d494e410 (sb_writers#8){.+.+}-{0:0}, at: mnt_want_write+0x44/0x9c fs/namespace.c:403

stack backtrace:
CPU: 1 PID: 6098 Comm: syz-executor324 Not tainted 6.6.0-rc4-syzkaller-g19af4a4ed414 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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:2060
 check_noncircular+0x310/0x404 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x3370/0x75e8 kernel/locking/lockdep.c:5136
 lock_acquire+0x23c/0x71c kernel/locking/lockdep.c:5753
 down_write_nested+0x58/0xcc kernel/locking/rwsem.c:1689
 inode_lock_nested include/linux/fs.h:837 [inline]
 filename_create+0x204/0x468 fs/namei.c:3889
 do_mkdirat+0xac/0x610 fs/namei.c:4135
 __do_sys_mkdirat fs/namei.c:4158 [inline]
 __se_sys_mkdirat fs/namei.c:4156 [inline]
 __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4156
 __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
 el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595


---
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#syz test: git://repo/address.git branch-or-commit-hash
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