[Freeipa-devel] [PATCH] detect failure to write ipa_kpasswd.pid file

[Jim Meyering]

Jim Meyering <jim at meyering.net> wrote:
> Making it more readable while retaining correctness is tricky.
> The catch lies in always closing F, even when fprintf fails.
> The following is shorter and no less correct -- maybe even more
> readable.  At least it doesn't set fail=1 three times:
> [note that technically, we should save errno from
>  a failed fprintf, so it can't be clobbered by fclose,
>  but in practice it probably doesn't matter, since that
>  use of fprintf won't ever fail. ]
>
> 	const char *pid_file = "/var/run/ipa_kpasswd.pid";
> 	int fail = 1;
> 	FILE *f = fopen(pid_file, "w");
> 	if (f) {
> 		int n_bytes = fprintf(f, "%ld\n", (long) getpid());
> 		if (fclose(f) == 0 && 0 < n_bytes)
> 			fail = 0;
> 	}
> 	if (fail) {
> 		syslog(LOG_ERR,"Couldn't create pid file %s: %s",
> 		       pid_file, strerror(errno));
> 		exit(1);
> 	}

In case you like that, here's the patch:

>From e9c342f7670c8120695e06351d3e895c2c907910 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering at redhat.com>
Date: Sun, 4 May 2008 15:17:36 +0200
Subject: [PATCH] detect failure to write ipa_kpasswd.pid file

* ipa_kpasswd.c (main): Detect not just open failure,
but also any write failure.
---
 ipa-server/ipa-kpasswd/ipa_kpasswd.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/ipa-server/ipa-kpasswd/ipa_kpasswd.c b/ipa-server/ipa-kpasswd/ipa_kpasswd.c
index 5782367..2b82f18 100644
--- a/ipa-server/ipa-kpasswd/ipa_kpasswd.c
+++ b/ipa-server/ipa-kpasswd/ipa_kpasswd.c
@@ -3,7 +3,7 @@

 /* Authors: Simo Sorce <ssorce at redhat.com>
  *
- * Copyright (C) 2007  Red Hat
+ * Copyright (C) 2007, 2008  Red Hat
  * see file 'COPYING' for use and warranty information
  *
  * This program is free software; you can redistribute it and/or
@@ -1188,13 +1188,18 @@ int main(int argc, char *argv[])
 	}

 	/* Write out the pid file after the sigterm handler */
-	FILE *f = fopen("/var/run/ipa_kpasswd.pid", "w");
-	if (f == NULL) {
-		syslog(LOG_ERR,"Couldn't create pid file /var/run/ipa_kpasswd.pid: %s", strerror(errno));
+	const char *pid_file = "/var/run/ipa_kpasswd.pid";
+	FILE *f = fopen(pid_file, "w");
+	int fail = 1;
+	if (f) {
+		int n_bytes = fprintf(f, "%ld\n", (long) getpid());
+		if (fclose(f) == 0 && 0 < n_bytes)
+			fail = 0;
+	}
+	if (fail) {
+		syslog(LOG_ERR,"Couldn't create pid file %s: %s",
+		       pid_file, strerror(errno));
 		exit(1);
-	} else {
-		fprintf(f, "%ld\n", (long) getpid());
-		fclose(f);
 	}

 	tai = ai;
--
1.5.5.1.216.g33c73