On Thu, Aug 17, 2017 at 09:23:10AM +0300, Dan Carpenter wrote:
> There are some potential integer overflows here on 64 bit systems.
>
> The condition "if (nfences > SIZE_MAX / sizeof(*fences))" can only be
> true on 32 bit systems, it's a no-op on 64 bit, so let's ignore the
> check for now and look a couple lines after:
>
> if (!access_ok(VERIFY_READ, user, nfences * 2 * sizeof(u32)))
> ^^^^^^^^^^^
> "nfences" is an unsigned int, so if we set it to UINT_MAX and multiply
> by two, it's going to have an integer overflow.
AFAICS it wouldn't overflow due the promotion to unsigned long
by '* sizeof(u32)'.
> The "args->buffer_count"
> is also an unsigned int so it could overflow if it's set to UINT_MAX
> when we do:
>
> exec2_list = kvmalloc_array(args->buffer_count + 1, sz,
> ^^^^^^^^^^^^^^^^^^^^^^
Yes, this could overflow.
> Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 15ab3e6792f9..f569721aad1a 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -2152,7 +2152,7 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
> if (!(args->flags & I915_EXEC_FENCE_ARRAY))
> return NULL;
>
> - if (nfences > SIZE_MAX / sizeof(*fences))
> + if (nfences > UINT_MAX / sizeof(*fences))
> return ERR_PTR(-EINVAL);
>
> user = u64_to_user_ptr(args->cliprects_ptr);
> @@ -2520,7 +2520,7 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
> unsigned int i;
> int err;
>
> - if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
> + if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
> DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
> return -EINVAL;
> }
> @@ -2609,7 +2609,7 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
> struct drm_syncobj **fences = NULL;
> int err;
>
> - if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
> + if (args->buffer_count < 1 || args->buffer_count > UINT_MAX / sz - 1) {
> DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
> return -EINVAL;
> }
> _______________________________________________
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