Re: [PATCH 1/3] gpg: Close stderr once finished with it in verify_signed_buffer()

[Jeff King <peff@peff.net>]

On Wed, Jan 30, 2013 at 06:01:04PM -0800, Stephen Boyd wrote:

> Failing to close the stderr pipe in verify_signed_buffer() causes
> git to run out of file descriptors if there are many calls to
> verify_signed_buffer(). An easy way to trigger this is to run
> 
>  git log --show-signature --merges | grep "key"
> 
> on the linux kernel git repo. Eventually it will fail with
> 
>  error: cannot create pipe for gpg: Too many open files
>  error: could not run gpg.
> 
> Close the stderr pipe so that this can't happen.

I was able to easily reproduce the bug and verify your fix here.

> diff --git a/gpg-interface.c b/gpg-interface.c
> index 0863c61..2c0bed3 100644
> --- a/gpg-interface.c
> +++ b/gpg-interface.c
> @@ -133,6 +133,8 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
>  	if (gpg_output)
>  		strbuf_read(gpg_output, gpg.err, 0);
>  	ret = finish_command(&gpg);
> +	if (gpg_output)
> +		close(gpg.err);

The strbuf_read above will read to EOF, so it should be equivalent (and
IMHO slightly more readable) to do:

diff --git a/gpg-interface.c b/gpg-interface.c
index 0863c61..5f142f6 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -130,8 +130,10 @@ int verify_signed_buffer(const char *payload, size_t payload_size,
 	write_in_full(gpg.in, payload, payload_size);
 	close(gpg.in);
 
-	if (gpg_output)
+	if (gpg_output) {
 		strbuf_read(gpg_output, gpg.err, 0);
+		close(gpg.err);
+	}
 	ret = finish_command(&gpg);
 
 	unlink_or_warn(path);

But that is a minor nit; either way, the patch looks good to me.

-Peff