From b68657fcec6ec4d13555d45666784be1a1f7393c Mon Sep 17 00:00:00 2001
From: "Kevin P. Fleming" <kpfleming@digium.com>
Date: Wed, 14 Sep 2005 22:40:54 +0000
Subject: [PATCH] ensure that ast_safe_system() is thread-safe (issue #4947)
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6603 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
asterisk.c | 48 ++++++++++++++++++++++++++++++++++--------------
1 file changed, 34 insertions(+), 14 deletions(-)
diff --git a/asterisk.c b/asterisk.c
index d251f666ba..7c74e67f17 100755
--- a/asterisk.c
+++ b/asterisk.c
@@ -349,42 +349,62 @@ static void null_sig_handler(int signal)
}
+AST_MUTEX_DEFINE_STATIC(safe_system_lock);
+static unsigned int safe_system_level = 0;
+static void *safe_system_prev_handler;
+
int ast_safe_system(const char *s)
{
- /* XXX This function needs some optimization work XXX */
pid_t pid;
int x;
int res;
struct rusage rusage;
int status;
- void (*prev_handler) = signal(SIGCHLD, null_sig_handler);
+ unsigned int level;
+
+ /* keep track of how many ast_safe_system() functions
+ are running at this moment
+ */
+ ast_mutex_lock(&safe_system_lock);
+ level = safe_system_level++;
+
+ /* only replace the handler if it has not already been done */
+ if (level == 0)
+ safe_system_prev_handler = signal(SIGCHLD, null_sig_handler);
+
+ ast_mutex_unlock(&safe_system_lock);
+
pid = fork();
+
if (pid == 0) {
/* Close file descriptors and launch system command */
- for (x=STDERR_FILENO + 1; x<4096;x++) {
+ for (x = STDERR_FILENO + 1; x < 4096; x++)
close(x);
- }
- res = execl("/bin/sh", "/bin/sh", "-c", s, NULL);
+ execl("/bin/sh", "/bin/sh", "-c", s, NULL);
exit(1);
} else if (pid > 0) {
for(;;) {
res = wait4(pid, &status, 0, &rusage);
if (res > -1) {
- if (WIFEXITED(status))
- res = WEXITSTATUS(status);
- else
- res = -1;
+ res = WIFEXITED(status) ? WEXITSTATUS(status) : -1;
+ break;
+ } else if (errno != EINTR)
break;
- } else {
- if (errno != EINTR)
- break;
- }
}
} else {
ast_log(LOG_WARNING, "Fork failed: %s\n", strerror(errno));
res = -1;
}
- signal(SIGCHLD, prev_handler);
+
+ ast_mutex_lock(&safe_system_lock);
+ level = --safe_system_level;
+
+ /* only restore the handler if we are the last one */
+ if (level == 0)
+ signal(SIGCHLD, safe_system_prev_handler);
+
+ ast_mutex_unlock(&safe_system_lock);
+
return res;
}
--
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