[PATCH] vringh: fix __vringh_iov() when riov and wiov are different

From: Stefano Garzarella <sgarzare@redhat.com>
To: mst@redhat.com
Cc: netdev@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>,
	stable@vger.kernel.org, Jason Wang <jasowang@redhat.com>
Subject: [PATCH] vringh: fix __vringh_iov() when riov and wiov are different
Date: Thu,  8 Oct 2020 18:13:11 +0200	[thread overview]
Message-ID: <20201008161311.114398-1-sgarzare@redhat.com> (raw)

If riov and wiov are both defined and they point to different
objects, only riov is initialized. If the wiov is not initialized
by the caller, the function fails returning -EINVAL and printing
"Readable desc 0x... after writable" error message.

Let's replace the 'else if' clause with 'if' to initialize both
riov and wiov if they are not NULL.

As checkpatch pointed out, we also avoid crashing the kernel
when riov and wiov are both NULL, replacing BUG() with WARN_ON()
and returning -EINVAL.

Fixes: f87d0fbb5798 ("vringh: host-side implementation of virtio rings.")
Cc: stable@vger.kernel.org
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 drivers/vhost/vringh.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index e059a9a47cdf..8bd8b403f087 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -284,13 +284,14 @@ __vringh_iov(struct vringh *vrh, u16 i,
 	desc_max = vrh->vring.num;
 	up_next = -1;
 
+	/* You must want something! */
+	if (WARN_ON(!riov && !wiov))
+		return -EINVAL;
+
 	if (riov)
 		riov->i = riov->used = 0;
-	else if (wiov)
+	if (wiov)
 		wiov->i = wiov->used = 0;
-	else
-		/* You must want something! */
-		BUG();
 
 	for (;;) {
 		void *addr;
-- 
2.26.2

