linux-kernel - Re: [PATCH] virtiofs: fix NULL dereference in virtio_fs_add_queues

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251215143207.GC19970@fedora>
Date: Mon, 15 Dec 2025 09:32:07 -0500
From: Stefan Hajnoczi <stefanha@...hat.com>
To: Qianchang Zhao <pioooooooooip@...il.com>
Cc: Vivek Goyal <vgoyal@...hat.com>, Miklos Szeredi <miklos@...redi.hu>,
	Eugenio Pérez <eperezma@...hat.com>,
	virtualization@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zhitong Liu <liuzhitong1993@...il.com>, stable@...r.kernel.org,
	Alok Tiwari <alok.a.tiwari@...cle.com>
Subject: Re: [PATCH] virtiofs: fix NULL dereference in
 virtio_fs_add_queues_sysfs()

On Sat, Dec 13, 2025 at 10:28:29AM +0900, Qianchang Zhao wrote:
> virtio_fs_add_queues_sysfs() creates per-queue sysfs kobjects via
> kobject_create_and_add(). The current code checks the wrong variable
> after the allocation:
> 
> - kobject_create_and_add() may return NULL on failure.
> - The code incorrectly checks fs->mqs_kobj (the parent kobject), which is
>   expected to be non-NULL at this point.
> - If kobject_create_and_add() fails, fsvq->kobj is NULL but the code can
>   still call sysfs_create_group(fsvq->kobj, ...), leading to a NULL pointer
>   dereference and kernel panic (DoS).
> 
> Fix by validating fsvq->kobj immediately after kobject_create_and_add()
> and aborting on failure, so sysfs_create_group() is never called with a
> NULL kobject.
> 
> Reported-by: Qianchang Zhao <pioooooooooip@...il.com>
> Reported-by: Zhitong Liu <liuzhitong1993@...il.com>
> Cc: stable@...r.kernel.org
> Signed-off-by: Qianchang Zhao <pioooooooooip@...il.com>
> ---
>  fs/fuse/virtio_fs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

This issue was fixed in October. It no longer exists in mainline Linux:

  commit c014021253d77cd89b2d8788ce522283d83fbd40
  Author: Alok Tiwari <alok.a.tiwari@...cle.com>
  Date:   Mon Oct 27 03:46:47 2025 -0700
  
      virtio-fs: fix incorrect check for fsvq->kobj

> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 6bc7c97b0..b2f6486fe 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -373,7 +373,7 @@ static int virtio_fs_add_queues_sysfs(struct virtio_fs *fs)
>  
>  		sprintf(buff, "%d", i);
>  		fsvq->kobj = kobject_create_and_add(buff, fs->mqs_kobj);
> -		if (!fs->mqs_kobj) {
> +		if (!fsvq->kobj) {
>  			ret = -ENOMEM;
>  			goto out_del;
>  		}
> -- 
> 2.34.1
> 

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)