linux-kernel - [PATCH v3] vduse: Fix off by one in vduse_dev

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Date: Wed, 28 Feb 2024 21:24:07 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Cindy Lu <lulu@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Xie Yongji <xieyongji@...edance.com>,
	Maxime Coquelin <maxime.coquelin@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Christian Brauner <brauner@...nel.org>,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH v3] vduse: Fix off by one in vduse_dev_mmap()

The dev->vqs[] array has "dev->vq_num" elements.  It's allocated in
vduse_dev_init_vqs().  Thus, this > comparison needs to be >= to avoid
reading one element beyond the end of the array.

Add an array_index_nospec() as well to prevent speculation issues.

Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
v2: add array_index_nospec()
v3: I accidentally corrupted v2.  Try again.

 drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index b7a1fb88c506..eb914084c650 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1532,9 +1532,10 @@ static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
 	if ((vma->vm_flags & VM_SHARED) == 0)
 		return -EINVAL;
 
-	if (index > dev->vq_num)
+	if (index >= dev->vq_num)
 		return -EINVAL;
 
+	index = array_index_nospec(index, dev->vq_num);
 	vq = dev->vqs[index];
 	vaddr = vq->vdpa_reconnect_vaddr;
 	if (vaddr == 0)
-- 
2.43.0