linux-kernel - [PATCH][next] drm/virtio: fix potential integer overflow on shift of a int

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Date:   Thu, 30 Sep 2021 11:19:41 +0100
From:   Colin King <colin.king@...onical.com>
To:     David Airlie <airlied@...ux.ie>, Gerd Hoffmann <kraxel@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Nicholas Verne <nverne@...omium.org>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/virtio: fix potential integer overflow on shift of a int

From: Colin Ian King <colin.king@...onical.com>

The left shift of unsigned int 32 bit integer constant 1 is evaluated
using 32 bit arithmetic and then assigned to a signed 64 bit integer.
In the case where i is 32 or more this can lead to an overflow. Fix
this by shifting the value 1ULL instead.

Addresses-Coverity: ("Uninitentional integer overflow")
Fixes: 8d6b006e1f51 ("drm/virtio: implement context init: handle VIRTGPU_CONTEXT_PARAM_POLL_RINGS_MASK")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 5618a1d5879c..b3b0557d72cf 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -819,7 +819,7 @@ static int virtio_gpu_context_init_ioctl(struct drm_device *dev,
 	if (vfpriv->ring_idx_mask) {
 		valid_ring_mask = 0;
 		for (i = 0; i < vfpriv->num_rings; i++)
-			valid_ring_mask |= 1 << i;
+			valid_ring_mask |= 1ULL << i;
 
 		if (~valid_ring_mask & vfpriv->ring_idx_mask) {
 			ret = -EINVAL;
-- 
2.32.0