drm/i915: Fix potential spectre vulnerability

commit 1a8e9bad6ef563c28ab0f8619628d5511be55431 upstream.

Fix smatch warning:
drivers/gpu/drm/i915/gem/i915_gem_context.c:847 set_proto_ctx_sseu()
warn: potential spectre issue 'pc->user_engines' [r] (local cap)

Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle create parameters (v5)")
Cc: <stable@vger.kernel.org> # v5.15+
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231103110922.430122-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit 27b086382c22efb7e0a16442f7bdc2e120108ef3)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 5980288..5e1b11d 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -844,6 +844,7 @@ static int set_proto_ctx_sseu(struct drm_i915_file_private *fpriv,
                if (idx >= pc->num_user_engines)
                        return -EINVAL;
 
+               idx = array_index_nospec(idx, pc->num_user_engines);
                pe = &pc->user_engines[idx];
 
                /* Only render engine supports RPCS configuration. */