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authorGustavo A. R. Silva <gustavo@embeddedor.com>2018-12-19 18:00:15 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-12-29 13:39:11 +0100
commitd04e6ea0cec9e7d6cba806508f657d2d0dc6cacf (patch)
treeaecfc9223407a18a55fb37506b028abef91491e3
parent5cebd962c97f3ee64555718169cc00c8fe7a228a (diff)
drm/ioctl: Fix Spectre v1 vulnerabilities
commit 505b5240329b922f21f91d5b5d1e535c805eca6d upstream. nr 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/drm_ioctl.c:805 drm_ioctl() warn: potential spectre issue 'dev->driver->ioctls' [r] drivers/gpu/drm/drm_ioctl.c:810 drm_ioctl() warn: potential spectre issue 'drm_ioctls' [r] (local cap) drivers/gpu/drm/drm_ioctl.c:892 drm_ioctl_flags() warn: potential spectre issue 'drm_ioctls' [r] (local cap) Fix this by sanitizing nr before using it to index dev->driver->ioctls and drm_ioctls. 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 Cc: stable@vger.kernel.org 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/20181220000015.GA18973@embeddedor Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/gpu/drm/drm_ioctl.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index a9ae6dd2d593..53f319369de5 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -37,6 +37,7 @@
#include <linux/pci.h>
#include <linux/export.h>
+#include <linux/nospec.h>
/**
* DOC: getunique and setversion story
@@ -778,13 +779,17 @@ long drm_ioctl(struct file *filp,
if (is_driver_ioctl) {
/* driver ioctl */
- if (nr - DRM_COMMAND_BASE >= dev->driver->num_ioctls)
+ unsigned int index = nr - DRM_COMMAND_BASE;
+
+ if (index >= dev->driver->num_ioctls)
goto err_i1;
- ioctl = &dev->driver->ioctls[nr - DRM_COMMAND_BASE];
+ index = array_index_nospec(index, dev->driver->num_ioctls);
+ ioctl = &dev->driver->ioctls[index];
} else {
/* core ioctl */
if (nr >= DRM_CORE_IOCTL_COUNT)
goto err_i1;
+ nr = array_index_nospec(nr, DRM_CORE_IOCTL_COUNT);
ioctl = &drm_ioctls[nr];
}
@@ -866,6 +871,7 @@ bool drm_ioctl_flags(unsigned int nr, unsigned int *flags)
if (nr >= DRM_CORE_IOCTL_COUNT)
return false;
+ nr = array_index_nospec(nr, DRM_CORE_IOCTL_COUNT);
*flags = drm_ioctls[nr].flags;
return true;