| Message ID | 20130311192716.GA18244@www.outflux.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Mar 11, 2013 at 12:27:16PM -0700, Kees Cook wrote: > It is possible to wrap the counter used to allocate the buffer for > relocation copies. This could lead to heap writing overflows. Seems a sensible check, just in the wrong location. You need to do the checking upfront in validate_exec_list() so that the error condition is always hit and that the limits are applied consistently to all execbuffers. -Chris
On Mon, Mar 11, 2013 at 1:52 PM, Chris Wilson <chris@chris-wilson.co.uk> wrote: > On Mon, Mar 11, 2013 at 12:27:16PM -0700, Kees Cook wrote: >> It is possible to wrap the counter used to allocate the buffer for >> relocation copies. This could lead to heap writing overflows. > > Seems a sensible check, just in the wrong location. You need to do the > checking upfront in validate_exec_list() so that the error condition is > always hit and that the limits are applied consistently to all > execbuffers. I opted for it here because it kept it out of the fast path which didn't need this check (it uses a list rather than an array). I will move it to validate_exec_list(). Thanks! -Kees -- Kees Cook Chrome OS Security
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c index 752e399..62eaa99 100644 --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c @@ -585,7 +585,8 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev, struct drm_i915_gem_object *obj; bool need_relocs; int *reloc_offset; - int i, total, ret; + int ret; + unsigned int i, total; int count = args->buffer_count; /* We may process another execbuffer during the unlock... */ @@ -600,8 +601,13 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev, mutex_unlock(&dev->struct_mutex); total = 0; - for (i = 0; i < count; i++) + for (i = 0; i < count; i++) { + if (exec[i].relocation_count > UINT_MAX - total) { + mutex_lock(&dev->struct_mutex); + return -ENOMEM; + } total += exec[i].relocation_count; + } reloc_offset = drm_malloc_ab(count, sizeof(*reloc_offset)); reloc = drm_malloc_ab(total, sizeof(*reloc));
It is possible to wrap the counter used to allocate the buffer for relocation copies. This could lead to heap writing overflows. Signed-off-by: Kees Cook <keescook@chromium.org> Reported-by: Pinkie Pie Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/i915_gem_execbuffer.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)