[PATCH AUTOSEL 4.14 42/52] Fix use after free in get_capset_info callback.

Sasha Levin
2020-10-18T19:34:39Z

From: Doug Horn <doughorn@google.com>

[ Upstream commit e219688fc5c3d0d9136f8d29d7e0498388f01440 ]

If a response to virtio_gpu_cmd_get_capset_info takes longer than
five seconds to return, the callback will access freed kernel memory
in vg->capsets.

Signed-off-by: Doug Horn <doughorn@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200902210847.2689-2-gurchetansingh@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/virtio/virtgpu_kms.c | 2 ++
drivers/gpu/drm/virtio/virtgpu_vq.c | 10 +++++++---
2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c
index 6400506a06b07..bed450fbb2168 100644
--- a/drivers/gpu/drm/virtio/virtgpu_kms.c
+++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
@@ -113,8 +113,10 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev,
vgdev->capsets[i].id > 0, 5 * HZ);
if (ret == 0) {
DRM_ERROR("timed out waiting for cap set %d\n", i);
+ spin_lock(&vgdev->display_info_lock);
kfree(vgdev->capsets);
vgdev->capsets = NULL;
+ spin_unlock(&vgdev->display_info_lock);
return;
}
DRM_INFO("cap set %d: id %d, max-version %d, max-size %d\n",
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index a3be65e689fd2..a956c73ea85e5 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -563,9 +563,13 @@ static void virtio_gpu_cmd_get_capset_info_cb(struct virtio_gpu_device *vgdev,
int i = le32_to_cpu(cmd->capset_index);

spin_lock(&vgdev->display_info_lock);
- vgdev->capsets[i].id = le32_to_cpu(resp->capset_id);
- vgdev->capsets[i].max_version = le32_to_cpu(resp->capset_max_version);
- vgdev->capsets[i].max_size = le32_to_cpu(resp->capset_max_size);
+ if (vgdev->capsets) {
+ vgdev->capsets[i].id = le32_to_cpu(resp->capset_id);
+ vgdev->capsets[i].max_version = le32_to_cpu(resp->capset_max_version);
+ vgdev->capsets[i].max_size = le32_to_cpu(resp->capset_max_size);
+ } else {
+ DRM_ERROR("invalid capset memory.");
+ }
spin_unlock(&vgdev->display_info_lock);
wake_up(&vgdev->resp_wq);
}
--
2.25.1