[Mesa-dev] [PATCH] mesa: prevent deleting the dummy ATI_fs

[Nicolai Hähnle]

On 01.11.2017 00:34, Miklós Máté wrote:
> This fixes a crash upon context destruction when
> glGenFragmentShadersATI() was used. Backtrace:
> ==15060== Invalid free() / delete / delete[] / realloc()
> ==15060==    at 0x482F478: free (vg_replace_malloc.c:530)
> ==15060==    by 0x57694F4: _mesa_delete_ati_fragment_shader (atifragshader.c:68)
> ==15060==    by 0x58B33AB: delete_fragshader_cb (shared.c:208)
> ==15060==    by 0x5838836: _mesa_HashDeleteAll (hash.c:295)
> ==15060==    by 0x58B365F: free_shared_state (shared.c:377)
> ==15060==    by 0x58B3BC2: _mesa_reference_shared_state (shared.c:469)
> ==15060==    by 0x578687F: _mesa_free_context_data (context.c:1366)
> ==15060==    by 0x595E9EC: st_destroy_context (st_context.c:642)
> ==15060==    by 0x5987057: st_context_destroy (st_manager.c:772)
> ==15060==    by 0x5B018B6: dri_destroy_context (dri_context.c:217)
> ==15060==    by 0x5B006D3: driDestroyContext (dri_util.c:511)
> ==15060==    by 0x4A1CBE6: dri3_destroy_context (dri3_glx.c:170)
> ==15060==  Address 0x7b5dae0 is 0 bytes inside data symbol "DummyShader"
> 
> This hasn't been an issue yet, because the only thing that calls
> glGenFragmentShadersATI() is my WIP piglit test. SWKOTOR and Doom3
> use hard-coded shader names.
> 
> The patch also fixes this:
> name=glGenFragmentShadersATI(1);
> glDeleteFragmentShaderATI(name);
> 
> Signed-off-by: Miklós Máté <mtmkls at gmail.com>
> ---
>   src/mesa/main/atifragshader.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mesa/main/atifragshader.c b/src/mesa/main/atifragshader.c
> index 27d8b86477..fdfaea0528 100644
> --- a/src/mesa/main/atifragshader.c
> +++ b/src/mesa/main/atifragshader.c
> @@ -60,6 +60,9 @@ void
>   _mesa_delete_ati_fragment_shader(struct gl_context *ctx, struct ati_fragment_shader *s)
>   {
>      GLuint i;
> +
> +   if (s == &DummyShader)
> +      return;
> +
>      for (i = 0; i < MAX_NUM_PASSES_ATI; i++) {
>         free(s->Instructions[i]);
>         free(s->SetupInst[i]);
> @@ -295,7 +298,6 @@ _mesa_DeleteFragmentShaderATI(GLuint id)
>         if (prog) {
>   	 prog->RefCount--;
>   	 if (prog->RefCount <= 0) {
> -	    assert(prog != &DummyShader);
>               _mesa_delete_ati_fragment_shader(ctx, prog);

This looks very much like it should be caught earlier by an error check. 
Usually, the object ID 0 is silently ignored by glDelete* commands (and 
negative values result in INVALID_VALUE).

Cheers,
Nicolai


>   	 }
>         }
> 


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