linux-kernel - Re: [syzbot] [fs?] [efi?] BUG: unable to handle kernel paging request in alloc_fs

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Message-ID: <CAMj1kXHHq=n=e9Dmw8uXoz+Tms2UZ7jtQtMMJvGCE6PW4muD5g@mail.gmail.com>
Date: Thu, 22 May 2025 15:47:43 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Christian Brauner <brauner@...nel.org>
Cc: syzbot <syzbot+52cd651546d11d2af06b@...kaller.appspotmail.com>, 
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, Al Viro <viro@...iv.linux.org.uk>, 
	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] [fs?] [efi?] BUG: unable to handle kernel paging request
 in alloc_fs_context

On Thu, 22 May 2025 at 14:24, Christian Brauner <brauner@...nel.org> wrote:
>
> On Wed, May 21, 2025 at 07:28:34PM +0200, Ard Biesheuvel wrote:
> > (cc James, Al, Christian)
> >
> > Please see the splat below.
> >
> > The NULL dereference is due to get_cred() in alloc_fs_context()
> > attempting to increment current->cred->usage while current->cred ==
> > NULL, and this is a result of the fact that PM notifier call chain is
> > called while the task is exiting.
> >
> > IIRC, the intent was for commit
> >
> >   11092db5b573 efivarfs: fix NULL dereference on resume
> >
> > to be replaced at some point with something more robust; might that
> > address this issue as well?
>
> Yes. It's in the merge queue for v6.16 which kills off all that
> vfs_kern_mount() stuff.

Excellent, thanks for the update.