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| author |   Gustavo A. R. Silva <gustavo@embeddedor.com> | 2018-12-19 18:00:15 -0600 |
|---|---|---|
| committer |   Daniel Vetter <daniel.vetter@ffwll.ch> | 2018-12-20 08:13:29 +0100 |
| commit | 505b5240329b922f21f91d5b5d1e535c805eca6d (patch) | |
| tree | 6ea8716b486fbe05a8b12de38d9ed814fcdbb1b3 | |
| parent | Linux 4.20-rc7 (diff) | |
| download | linux-dev-505b5240329b922f21f91d5b5d1e535c805eca6d.tar.xz linux-dev-505b5240329b922f21f91d5b5d1e535c805eca6d.zip | |
drm/ioctl: Fix Spectre v1 vulnerabilities
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
| -rw-r--r-- | drivers/gpu/drm/drm_ioctl.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 94bd872d56c4..7e6746b2d704 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 @@ -800,13 +801,17 @@ 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]; } @@ -888,6 +893,7 @@ 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; |