On Thu, Apr 02, 2020 at 07:34:18AM +0000, Christophe Leroy wrote:
> When i915_gem_execbuffer2_ioctl() is using user_access_begin(),
> that's only to perform unsafe_put_user() so use
> user_write_access_begin() in order to only open write access.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Why is this split from the other conversions?
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 7643a30ba4cd..4be8205a70b6 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -1611,14 +1611,14 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb)
> * happened we would make the mistake of assuming that the
> * relocations were valid.
> */
> - if (!user_access_begin(urelocs, size))
> + if (!user_write_access_begin(urelocs, size))
> goto end;
>
> for (copied = 0; copied < nreloc; copied++)
> unsafe_put_user(-1,
> &urelocs[copied].presumed_offset,
> end_user);
> - user_access_end();
> + user_write_access_end();
>
> eb->exec[i].relocs_ptr = (uintptr_t)relocs;
> }
> @@ -1626,7 +1626,7 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb)
> return 0;
>
> end_user:
> - user_access_end();
> + user_write_access_end();
> end:
> kvfree(relocs);
> err = -EFAULT;
> @@ -2991,7 +2991,8 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
> * And this range already got effectively checked earlier
> * when we did the "copy_from_user()" above.
> */
> - if (!user_access_begin(user_exec_list, count * sizeof(*user_exec_list)))
> + if (!user_write_access_begin(user_exec_list,
> + count * sizeof(*user_exec_list)))
> goto end;
>
> for (i = 0; i < args->buffer_count; i++) {
> @@ -3005,7 +3006,7 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
> end_user);
> }
> end_user:
> - user_access_end();
> + user_write_access_end();
> end:;
> }
>
> --
> 2.25.0
>
--
Kees Cook
