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Date: Thu, 22 May 2025 14:24:10 +0200
From: Christian Brauner <brauner@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: syzbot <syzbot+52cd651546d11d2af06b@syzkaller.appspotmail.com>, 
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>, Al Viro <viro@zeniv.linux.org.uk>, 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] [fs?] [efi?] BUG: unable to handle kernel paging
 request in alloc_fs_context
Message-ID: <20250522-exotisch-chloren-3fa7b7ce5266@brauner>
References: <6820e1f6.050a0220.f2294.003c.GAE@google.com>
 <CAMj1kXEg88Q5GCV+YW13UT4eDEzMpnKW8ReJNDjLqX7xeXaw=w@mail.gmail.com>
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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.