drm/bufs: Fix Spectre v1 vulnerability
Subsystems (2)
PATCH 1/1 drm/bufs: Fix Spectre v1 vulnerability
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
--- drivers/gpu/drm/drm_bufs.c | 3 +++ 1 file changed, 3 insertions(+)
drivers/gpu/drm/drm_bufs.c +3 -0
@@ -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) {
@@ -1417,6 +1419,7 @@ 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",
Signature · 1 line
2.7.4
Quoted 10 lines · Gustavo A. R. Silva
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:1420drm_legacy_freebufs()warn: potential spectre issue 'dma->buflist' [r] (local cap)Fix this by sanitizing idx before using it to index
dma->buflist
Quoted 8 lines
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 <[email protected]>
Applied since it's correct, but I dropped the cc: stable. This code is very dead and full of security issues, and spectre is the least of your worries. If you want to a stab at fixing the real spectre issues in drm, then look anywhere that isn't full of drm_legacy_* functions.
The most important file is probably drm_ioctl.c.
-Daniel
Quoted 32 lines
--- drivers/gpu/drm/drm_bufs.c | 3 +++ 1 file changed, 3 insertions(+)drivers/gpu/drm/drm_bufs.c +3
-0@@ -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) {@@ -1417,6 +1419,7 @@ 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",Signature · 6 lines
2.7.4 _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
Signature · 3 lines
Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
Quoted 8 lines · Daniel Vetter
Quoted 2 lines
Signed-off-by Gustavo A. R. Silva <[email protected]>Applied since it's correct, but I dropped the cc: stable. This code is very dead and full of security issues, and spectre is the least of your worries. If you want to a stab at fixing the real spectre issues in drm, then look anywhere that isn't full of drm_legacy_* functions.
OK. I've got it.
Quoted 3 lines
The most important file is probably
drm_ioctl.c.
-Daniel
Thanks for the feedback, Daniel.
--
Gustavo