drm: Prevent overwriting from userspace underallocating core ioctl structs

Apply the protections from

commit 1b2f1489633888d4a06028315dc19d65768a1c05
Author: Dave Airlie <airlied@redhat.com>
Date:   Sat Aug 14 20:20:34 2010 +1000

    drm: block userspace under allocating buffer and having drivers overwrite it (v2)

to the core ioctl structs as well, for we found one instance where there
is a 32-/64-bit size mismatch and were guilty of writing beyond the end
of the user's buffer.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index e572dd20bdee..05ad9ba0a67e 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -402,9 +402,16 @@ long drm_ioctl(struct file *filp,
                 cmd = ioctl->cmd_drv;
         }
         else if ((nr >= DRM_COMMAND_END) || (nr < DRM_COMMAND_BASE)) {
+                u32 drv_size;
+
                 ioctl = &drm_ioctls[nr];
-                cmd = ioctl->cmd;
+
+                drv_size = _IOC_SIZE(ioctl->cmd);
                 usize = asize = _IOC_SIZE(cmd);
+                if (drv_size > asize)
+                        asize = drv_size;
+
+                cmd = ioctl->cmd;
         } else
                 goto err_i1;