Re: [syzbot] [efi?] [fs?] possible deadlock in efivarfs_actor

Ard Biesheuvel
2025-03-10T07:21:49Z

(cc James)

On Sun, 9 Mar 2025 at 03:52, syzbot
<syzbot+019072ad24ab1d948228@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e056da87c780 Merge remote-tracking branch 'will/for-next/p..
> 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=14ce9c64580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d6b7e15dc5b5e776
> dashboard link: https://syzkaller.appspot.com/bug?extid=019072ad24ab1d948228
> 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=111ed7a0580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13b97c64580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3d8b1b7cc4c0/disk-e056da87.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b84c04cff235/vmlinux-e056da87.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/2ae4d0525881/Image-e056da87.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+019072ad24ab1d948228@syzkaller.appspotmail.com
>
> efivarfs: resyncing variable state
> ============================================
> WARNING: possible recursive locking detected
> 6.14.0-rc4-syzkaller-ge056da87c780 #0 Not tainted
> --------------------------------------------
> syz-executor772/6443 is trying to acquire lock:
> ffff0000c6826558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline]
> ffff0000c6826558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: efivarfs_actor+0x1b8/0x2b8 fs/efivarfs/super.c:422
>
> but task is already holding lock:
> ffff0000c6c7a558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: iterate_dir+0x3b4/0x5f4 fs/readdir.c:101
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&sb->s_type->i_mutex_key#16);
> lock(&sb->s_type->i_mutex_key#16);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 3 locks held by syz-executor772/6443:
> #0: ffff80008fc57208 (system_transition_mutex){+.+.}-{4:4}, at: lock_system_sleep+0x68/0xc0 kernel/power/main.c:56
> #1: ffff80008fc75d70 ((pm_chain_head).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x58/0xa0 kernel/notifier.c:379
> #2: ffff0000c6c7a558 (&sb->s_type->i_mutex_key#16){++++}-{4:4}, at: iterate_dir+0x3b4/0x5f4 fs/readdir.c:101
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 6443 Comm: syz-executor772 Not tainted 6.14.0-rc4-syzkaller-ge056da87c780 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
> Call trace:
> show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
> __dump_stack lib/dump_stack.c:94 [inline]
> dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:120
> dump_stack+0x1c/0x28 lib/dump_stack.c:129
> print_deadlock_bug+0x4e8/0x668 kernel/locking/lockdep.c:3039
> check_deadlock kernel/locking/lockdep.c:3091 [inline]
> validate_chain kernel/locking/lockdep.c:3893 [inline]
> __lock_acquire+0x6240/0x7904 kernel/locking/lockdep.c:5228
> lock_acquire+0x23c/0x724 kernel/locking/lockdep.c:5851
> down_write+0x50/0xc0 kernel/locking/rwsem.c:1577
> inode_lock include/linux/fs.h:877 [inline]
> efivarfs_actor+0x1b8/0x2b8 fs/efivarfs/super.c:422
> dir_emit include/linux/fs.h:3849 [inline]
> dcache_readdir+0x2dc/0x4e8 fs/libfs.c:209
> iterate_dir+0x46c/0x5f4 fs/readdir.c:108
> efivarfs_pm_notify+0x2f4/0x350 fs/efivarfs/super.c:517
> notifier_call_chain+0x1c4/0x550 kernel/notifier.c:85
> blocking_notifier_call_chain+0x70/0xa0 kernel/notifier.c:380
> pm_notifier_call_chain+0x2c/0x3c kernel/power/main.c:109
> snapshot_release+0x128/0x1b8 kernel/power/user.c:125
> __fput+0x340/0x760 fs/file_table.c:464
> ____fput+0x20/0x30 fs/file_table.c:492
> task_work_run+0x230/0x2e0 kernel/task_work.c:227
> resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
> do_notify_resume+0x178/0x1f4 arch/arm64/kernel/entry-common.c:151
> exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
> exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
> el0_svc+0xac/0x168 arch/arm64/kernel/entry-common.c:745
> el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762
> el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600
>
>
> ---
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