cluster: STABLE32 - liblogthread: Avoid potetntial race when changing log files

[Christine Caulfield]

Gitweb:        http://git.fedorahosted.org/git/?p=cluster.git;a=commitdiff;h=9d6a1843fefe07...
Commit:        9d6a1843fefe0799065afbe5d0a7637fed6887fc
Parent:        2f05327bd8e7a072418dca45988ab5a814109258
Author:        Christine Caulfield 
AuthorDate:    Thu Oct 30 09:43:35 2014 +0000
Committer:     Christine Caulfield 
CommitterDate: Thu Oct 30 09:43:35 2014 +0000

liblogthread: Avoid potetntial race when changing log files

There is a potential for a crash when a log file is changed or
re-opened as the fclose can happen in the main thread while the
writing thread is about to output data.

This patch avoids that by allocating a new fp for the new file and
only closing the old fp* later one when the thread holds the lock.

Signed-off-by: Christine Caulfield 
---
 common/liblogthread/liblogthread.c |   36 +++++++++++++++++++++++++++---------
 1 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/common/liblogthread/liblogthread.c b/common/liblogthread/liblogthread.c
index 088d171..b44f01a 100644
--- a/common/liblogthread/liblogthread.c
+++ b/common/liblogthread/liblogthread.c
@@ -38,6 +38,7 @@ static int logt_logfile_priority;
 static char logt_name[PATH_MAX];
 static char logt_logfile[PATH_MAX];
 static FILE *logt_logfile_fp;
+static FILE *new_logt_logfile_fp;

static char *_time(time_t *t)
 {
@@ -100,6 +101,13 @@ static void *thread_fn(void *arg)

prev_dropped = dropped;
    	dropped = 0;
+
+		if (new_logt_logfile_fp) {
+		       fclose(logt_logfile_fp);
+		       logt_logfile_fp = new_logt_logfile_fp;
+		       new_logt_logfile_fp = NULL;
+		}
+
    	pthread_mutex_unlock(&mutex);

if (prev_dropped) {
@@ -176,20 +184,30 @@ static void _conf(const char *name, int mode, int syslog_facility,
    	strncpy(logt_logfile, logfile, PATH_MAX - 1);

if (logt_mode & LOG_MODE_OUTPUT_FILE && logt_logfile[0]) {
-		if (logt_logfile_fp) {
-			fclose(logt_logfile_fp);
-			logt_logfile_fp = NULL;
-		}
-		logt_logfile_fp = fopen(logt_logfile, "a+");
-		if (logt_logfile_fp != NULL) {
-			fd = fileno(logt_logfile_fp);
-			fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
-		}
+	       /* Don't close the existing fp in this thread, let the main logthread do it later */
+	       if (!logt_logfile_fp) {
+		      logt_logfile_fp = fopen(logt_logfile, "a+");
+		      if (logt_logfile_fp != NULL) {
+			     fd = fileno(logt_logfile_fp);
+			     fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+		      }
+	       }
+	       else {
+		      new_logt_logfile_fp = fopen(logt_logfile, "a+");
+		      if (new_logt_logfile_fp != NULL) {
+			     fd = fileno(new_logt_logfile_fp);
+			     fcntl(fd, F_SETFD, fcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
+		      }
+	       }
    } else {
    	if (logt_logfile_fp) {
    		fclose(logt_logfile_fp);
    		logt_logfile_fp = NULL;
    	}
+		if (new_logt_logfile_fp) {
+			fclose(new_logt_logfile_fp);
+			new_logt_logfile_fp = NULL;
+		}
    }

if (logt_mode & LOG_MODE_OUTPUT_SYSLOG) {