On 04.05.2017 23:18, Bartosz Tomczyk wrote:
malloc can return valid pointer for zero size allocation,
which causes OOB access later on

v2: Return error if count is 0, clear previous shader source
---
 src/mesa/main/shaderapi.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/mesa/main/shaderapi.c b/src/mesa/main/shaderapi.c
index c41f006eb7..b39b7fd1c4 100644
--- a/src/mesa/main/shaderapi.c
+++ b/src/mesa/main/shaderapi.c
@@ -1009,7 +1009,8 @@ shader_source(struct gl_shader *sh, const GLchar *source)
    }

 #ifdef DEBUG
-   sh->SourceChecksum = util_hash_crc32(sh->Source, strlen(sh->Source));
+   sh->SourceChecksum = sh->Source ?
+      util_hash_crc32(sh->Source, strlen(sh->Source)) : 0xFFFFFFFF;
 #endif
 }

@@ -1780,7 +1781,8 @@ _mesa_ShaderSource(GLuint shaderObj, GLsizei count,
    if (!sh)
       return;

-   if (string == NULL) {
+   if (string == NULL || count == 0) {
+      shader_source(sh, NULL);
       _mesa_error(ctx, GL_INVALID_VALUE, "glShaderSourceARB");
       return;
    }

NAK, for two reasons:

1. Neither of these error conditions is actually documented in the OpenGL spec as far as I can tell; the whole if-statement should be removed. As far as I can tell, passing string == NULL && count == 0 is valid, and should be equivalent to setting an empty source string.

2. When an OpenGL error other than GL_OUT_OF_MEMORY is flagged, the state of the GL context *must* remain unchanged.

I think replacing the whole thing with

   if (count == 0) {
      shader_source(sh, NULL);
      return;
   }

is fine.

Cheers,
Nicolai
--
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.
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