linux-kernel - Re: [syzbot] [efi?] [fs?] possible deadlock in efivarfs

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Message-ID: <20250310235831.GL2023217@ZenIV>
Date: Mon, 10 Mar 2025 23:58:31 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: James Bottomley <James.Bottomley@...senpartnership.com>,
	syzbot <syzbot+019072ad24ab1d948228@...kaller.appspotmail.com>,
	jk@...abs.org, linux-efi@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [efi?] [fs?] possible deadlock in efivarfs_actor

On Mon, Mar 10, 2025 at 07:21:53PM +0100, Ard Biesheuvel wrote:

> The repro log also has
> 
> program crashed: BUG: unable to handle kernel paging request in
> efivarfs_pm_notify
> 
> preceding the other log output regarding the locks, so the deadlock
> might be a symptom of another problem.

This:
        struct path path = { .mnt = NULL, .dentry = sfi->sb->s_root, };

_What_ .mnt = NULL?  That's already a bug.  There is no such thing
as mountless open file; how would the kernel know not to shut the
damn thing down right under you?