Looks good to me based on my limited understanding. Thomas/Sinclair can could you please review and then we can include this in drm-fixes.
Thanks, Deepak
arg.version is 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/vmwgfx/vmwgfx_execbuf.c:4526 vmw_execbuf_ioctl() warn: potential spectre issue 'copy_offset' [w]
Fix this by sanitizing arg.version before using it to index copy_offset
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://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmarc.i nfo%2F%3Fl%3Dlinux- kernel%26m%3D152449131114778%26w%3D2&data=02%7C01%7Clinux- graphics- maintainer%40vmware.com%7Cf010b707b8ef4896c1a908d603aebcc6%7Cb39 138ca3cee4b4aa4d6cd83d9dd62f0%7C1%7C0%7C636700446365603728& sdata=0D8lnUScxOmCCWXLHh8Otc3o%2F1yF1SxgGwIklRdMlXY%3D&re served=0
Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com
drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c index 1f13457..ad91c6e 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c @@ -25,6 +25,7 @@
****************/ #include <linux/sync_file.h> +#include <linux/nospec.h>
#include "vmwgfx_drv.h" #include "vmwgfx_reg.h" @@ -4520,8 +4521,10 @@ int vmw_execbuf_ioctl(struct drm_device *dev, unsigned long data, return -EINVAL; }
- if (arg.version > 1 &&
copy_from_user(&arg.context_handle,
- if (arg.version >= ARRAY_SIZE(copy_offset))
return -EFAULT;- arg.version = array_index_nospec(arg.version,
ARRAY_SIZE(copy_offset));
- if (copy_from_user(&arg.context_handle, (void __user *) (data + copy_offset[0]), copy_offset[arg.version - 1] - copy_offset[0]) != 0)
-- 2.7.4
Sent to linux-graphics-maintainer@vmware.com