linux-kernel - Re: [PATCH 05/24] perf daemon: Add client socket support

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Date:   Thu, 11 Feb 2021 09:52:05 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Alexei Budankov <abudankov@...wei.com>
Subject: Re: [PATCH 05/24] perf daemon: Add client socket support

Em Mon, Feb 08, 2021 at 09:08:49PM +0100, Jiri Olsa escreveu:
> +__maybe_unused
> +static int send_cmd(struct daemon *daemon, union cmd *cmd)
> +{
> +	int ret = -1, fd;
> +	char *line = NULL;
> +	size_t len = 0;
> +	ssize_t nread;
> +	FILE *in = NULL;
> +
> +	if (setup_client_config(daemon))
> +		return -1;
> +
> +	fd = setup_client_socket(daemon);
> +	if (fd < 0)
> +		return -1;
> +
> +	if (sizeof(*cmd) != writen(fd, cmd, sizeof(*cmd))) {
> +		perror("failed: write");
> +		goto out;
> +	}
> +
> +	in = fdopen(fd, "r");
> +	if (!in) {
> +		perror("failed: fdopen");
> +		goto out;
> +	}
> +
> +	while ((nread = getline(&line, &len, in)) != -1) {
> +		fwrite(line, nread, 1, stdout);
> +		fflush(stdout);
> +	}
> +
> +	ret = 0;
> +	fclose(in);
> +out:
> +	/* If in is defined, then fd is closed via fclose. */
> +	if (!in)
> +		close(fd);
> +	return ret;
> +}
> +

So I had to add the patch below to deal with this in some systems:

  cc1: warnings being treated as errors
  builtin-daemon.c: In function 'send_cmd':  MKDIR    /tmp/build/perf/bench/
  
  builtin-daemon.c:1368: error: ignoring return value of 'fwrite', declared with attribute warn_unused_result
    MKDIR    /tmp/build/perf/tests/
  make[3]: *** [/tmp/build/perf/builtin-daemon.o] Error 1

And also to not leak the 'line' buffer allocated by getline(), since you
initialized line to NULL and len to zero, man page says:

	 If *lineptr is set to NULL and *n is set 0 before the call,
	 then getline() will allocate a buffer for storing the line.
	 This buffer should be freed by the user program even if
	 getline() failed.


diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
index e0880c5ee39c89bd..0a282c4e23a9fd9a 100644
--- a/tools/perf/builtin-daemon.c
+++ b/tools/perf/builtin-daemon.c
@@ -344,12 +344,15 @@ static int send_cmd(struct daemon *daemon, union cmd *cmd)
 	}
 
 	while ((nread = getline(&line, &len, in)) != -1) {
-		fwrite(line, nread, 1, stdout);
+		if (fwrite(line, nread, 1, stdout) != 1)
+			goto out_fclose;
 		fflush(stdout);
 	}
 
 	ret = 0;
+out_fclose:
 	fclose(in);
+	free(line);
 out:
 	/* If in is defined, then fd is closed via fclose. */
 	if (!in)