| From c9c8e4384dd822b463b8df56f8e415f265fd3c05 Mon Sep 17 00:00:00 2001 |
| From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> |
| Date: Tue, 16 Oct 2018 11:55:49 +0200 |
| Subject: drm/bufs: Fix Spectre v1 vulnerability |
| |
| [ Upstream commit a37805098900a6e73a55b3a43b7d3bcd987bb3f4 ] |
| |
| idx can be indirectly controlled by user-space, hence leading to a |
| potential exploitation of the Spectre variant 1 vulnerability. |
| |
| This issue was detected with the help of Smatch: |
| |
| drivers/gpu/drm/drm_bufs.c:1420 drm_legacy_freebufs() warn: potential |
| spectre issue 'dma->buflist' [r] (local cap) |
| |
| Fix this by sanitizing idx before using it to index dma->buflist |
| |
| Notice that given that speculation windows are large, the policy is |
| to kill the speculation on the first load and not worry if it can be |
| completed with a dependent load/store [1]. |
| |
| [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 |
| |
| Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Link: https://patchwork.freedesktop.org/patch/msgid/20181016095549.GA23586@embeddedor.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| drivers/gpu/drm/drm_bufs.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c |
| index f1a204d253cc..ac22b8d86249 100644 |
| --- a/drivers/gpu/drm/drm_bufs.c |
| +++ b/drivers/gpu/drm/drm_bufs.c |
| @@ -36,6 +36,8 @@ |
| #include <drm/drmP.h> |
| #include "drm_legacy.h" |
| |
| +#include <linux/nospec.h> |
| + |
| static struct drm_map_list *drm_find_matching_map(struct drm_device *dev, |
| struct drm_local_map *map) |
| { |
| @@ -1332,6 +1334,7 @@ int drm_legacy_freebufs(struct drm_device *dev, void *data, |
| idx, dma->buf_count - 1); |
| return -EINVAL; |
| } |
| + idx = array_index_nospec(idx, dma->buf_count); |
| buf = dma->buflist[idx]; |
| if (buf->file_priv != file_priv) { |
| DRM_ERROR("Process %d freeing buffer not owned\n", |
| -- |
| 2.19.1 |
| |
