[Mesa-dev] [PATCH] swr/rast: do not crash on NULL strings returned by getenv

[Eric Engestrom]

On Monday, 2017-09-18 11:29:21 +0100, Emil Velikov wrote:
> From: Bernhard Rosenkraenzer <bero at lindev.ch>
> 
> The current convinince function GetEnv feeds the results of getenv
> directly into std::string(). That is a bad idea, since the variable
> may be unset, thus we feed NULL into the C++ construct.
> 
> The latter of which is not allowed and leads to a crash.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101832
> Fixes: a25093de718 ("swr/rast: Implement JIT shader caching to disk")
> Cc: Tim Rowley <timothy.o.rowley at intel.com>
> Cc: Laurent Carlier <lordheavym at gmail.com>
> Cc: Bernhard Rosenkraenzer <bero at lindev.ch>
> [Emil Velikov: make an actual commit from the misc diff]
> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>

Laurent just sent this to the ML an hour before you, but this commit
message is much better.

Reviewed-by: Eric Engestrom <eric.engestrom at imgtec.com>

> ---
>  src/gallium/drivers/swr/rasterizer/core/utils.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/gallium/drivers/swr/rasterizer/core/utils.h b/src/gallium/drivers/swr/rasterizer/core/utils.h
> index b096d2120cb..3c849e82d3b 100644
> --- a/src/gallium/drivers/swr/rasterizer/core/utils.h
> +++ b/src/gallium/drivers/swr/rasterizer/core/utils.h
> @@ -365,7 +365,8 @@ static INLINE std::string GetEnv(const std::string& variableName)
>      output.resize(valueSize - 1); // valueSize includes null, output.resize() does not
>      GetEnvironmentVariableA(variableName.c_str(), &output[0], valueSize);
>  #else
> -    output = getenv(variableName.c_str());
> +    char *o = getenv(variableName.c_str());
> +    output = o ? std::string(o) : std::string();

Like I mentioned [2] on his patch, I think this could be written
better, eg:

	char *env = getenv(variableName.c_str());
	output = env ? env : "";

[1] https://lists.freedesktop.org/archives/mesa-dev/2017-September/169977.html
[2] https://lists.freedesktop.org/archives/mesa-dev/2017-September/169996.html

>  #endif
>  
>      return output;
> -- 
> 2.14.1
>