[Mesa-dev] [PATCH 4/4] aux/pipe_loader: Don't leak dlerror string on dlopen failure

[Ilia Mirkin]

On Thu, Nov 13, 2014 at 6:43 PM, Aaron Watry <awatry at gmail.com> wrote:
> dlopen allocates a string on dlopen failure which is retrieved via dlerror. In
> order to free that string, you need to retrieve and then free it.

Are you basically saying that glibc leaks memory and you're trying to
make up for it? What if you use a non-buggy library? Or is dlopen()
specified in such a way that if it fails, you must free the result of
dlerror? I see nothing in the man pages to suggest that...

>
> In order to keep things legit the windows/other util_dl_error paths allocate
> and then copy their error message into a buffer as well.
>
> Signed-off-by: Aaron Watry <awatry at gmail.com>
> CC: Ilia Mirkin <imirkin at alum.mit.edu>
>
> v3: Switch comment to C-Style
> v2: Use strdup instead of calloc/strcpy
> ---
>  src/gallium/auxiliary/pipe-loader/pipe_loader.c | 5 +++++
>  src/gallium/auxiliary/util/u_dl.c               | 4 ++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/src/gallium/auxiliary/pipe-loader/pipe_loader.c b/src/gallium/auxiliary/pipe-loader/pipe_loader.c
> index 8e79f85..7a4e0b1 100644
> --- a/src/gallium/auxiliary/pipe-loader/pipe_loader.c
> +++ b/src/gallium/auxiliary/pipe-loader/pipe_loader.c
> @@ -25,6 +25,8 @@
>   *
>   **************************************************************************/
>
> +#include <dlfcn.h>
> +
>  #include "pipe_loader_priv.h"
>
>  #include "util/u_inlines.h"
> @@ -101,6 +103,9 @@ pipe_loader_find_module(struct pipe_loader_device *dev,
>           if (lib) {
>              return lib;
>           }
> +
> +         /* Retrieve the dlerror() str so that it can be freed properly */
> +         FREE(util_dl_error());
>        }
>     }
>
> diff --git a/src/gallium/auxiliary/util/u_dl.c b/src/gallium/auxiliary/util/u_dl.c
> index aca435d..00c4d7c 100644
> --- a/src/gallium/auxiliary/util/u_dl.c
> +++ b/src/gallium/auxiliary/util/u_dl.c
> @@ -87,8 +87,8 @@ util_dl_error(void)
>  #if defined(PIPE_OS_UNIX)
>     return dlerror();
>  #elif defined(PIPE_OS_WINDOWS)
> -   return "unknown error";
> +   return strdup("unknown error");
>  #else
> -   return "unknown error";
> +   return strdup("unknown error");
>  #endif
>  }
> --
> 2.1.0
>