[PATCH v2] drm/vc4: fix krealloc() memory leak

[Alexander A. Klimov]

Don't just overwrite the original pointer passed to krealloc()
with its return value without checking latter:

    MEM = krealloc(MEM, SZ, GFP);

If krealloc() returns NULL, that erases the pointer
to the still allocated memory, hence leaks this memory.
Instead, use a temporary variable, check it's not NULL
and only then assign it to the original pointer:

    TMP = krealloc(MEM, SZ, GFP);
    if (!TMP) return;
    MEM = TMP;

Fixes: 6d45c81d229d ("drm/vc4: Add support for branching in shader validation.")
Signed-off-by: Alexander A. Klimov <grandmaster@xxxxxxxxxxxx>
---
 v2: Declare the variable explicitly
 v2: Instead of void *, use u32 *
 v2: While on it, enhance variable name

 [✓] scripts/checkpatch.pl --strict
 [✓] allmodconfig compiled (i686, LLVM)
 [✓] localyesconfig booted (IBM T43)

 Note to myself: use --in-reply-to=2b602ec6-d563-4fa0-a0c5-89b97a46abf9@xxxxxxxxxx

 drivers/gpu/drm/vc4/vc4_validate_shaders.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
index d48cf76983c0..6f52b4db9cc9 100644
--- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c
+++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
@@ -290,15 +290,16 @@ static bool require_uniform_address_uniform(struct vc4_validated_shader_info *va
 {
 	uint32_t o = validated_shader->num_uniform_addr_offsets;
 	uint32_t num_uniforms = validated_shader->uniforms_size / 4;
+	u32 *offsets;
 
-	validated_shader->uniform_addr_offsets =
-		krealloc(validated_shader->uniform_addr_offsets,
-			 (o + 1) *
-			 sizeof(*validated_shader->uniform_addr_offsets),
-			 GFP_KERNEL);
-	if (!validated_shader->uniform_addr_offsets)
+	offsets = krealloc(validated_shader->uniform_addr_offsets,
+			   (o + 1) *
+			   sizeof(*validated_shader->uniform_addr_offsets),
+			   GFP_KERNEL);
+	if (!offsets)
 		return false;
 
+	validated_shader->uniform_addr_offsets = offsets;
 	validated_shader->uniform_addr_offsets[o] = num_uniforms;
 	validated_shader->num_uniform_addr_offsets++;
 
-- 
2.54.0