From: Al Viro <viro@zeniv.linux.org.uk>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
syzbot <syzbot+019072ad24ab1d948228@syzkaller.appspotmail.com>,
jk@ozlabs.org, linux-efi@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [efi?] [fs?] possible deadlock in efivarfs_actor
Date: Mon, 10 Mar 2025 23:25:30 +0000 [thread overview]
Message-ID: <20250310232530.GK2023217@ZenIV> (raw)
In-Reply-To: <CAMj1kXEfG=Q3pk6PsVZxf5qCjEBTwTjUCJcNwBPO3PqNmSp=hw@mail.gmail.com>
On Mon, Mar 10, 2025 at 07:24:43PM +0100, Ard Biesheuvel wrote:
> And one of the other logs has
>
> [ 47.650966][ T6617] syz.2.9/6617 is trying to acquire lock:
> [ 47.652339][ T6617] ffff0000d69f6558
> (&sb->s_type->i_mutex_key#25){++++}-{4:4}, at:
> efivarfs_actor+0x1b8/0x2b8
> [ 47.654943][ T6617]
> [ 47.654943][ T6617] but task is already holding lock:
> [ 47.656931][ T6617] ffff0000f5b84558
> (&sb->s_type->i_mutex_key#25){++++}-{4:4}, at: iterate_dir+0x3b4/0x5f4
>
> where the locks have the same name but the address is different.
>
> So there is something dodgy going on here, and I'm inclined to just ignore it.
That one is a false positive - iterate_dir() locks parent, then
callback locks child, but without bothering to tell lockdep about
that. IOW, in actor you should use inode_lock_nested(inode, INODE_CHILD);
instead of inode_lock(inode).
next prev parent reply other threads:[~2025-03-10 23:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-09 2:52 [syzbot] [efi?] [fs?] possible deadlock in efivarfs_actor syzbot
2025-03-10 7:21 ` Ard Biesheuvel
2025-03-10 16:50 ` James Bottomley
2025-03-10 18:21 ` Ard Biesheuvel
2025-03-10 18:24 ` Ard Biesheuvel
2025-03-10 23:25 ` Al Viro [this message]
2025-03-10 23:58 ` Al Viro
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