From: Martin Wilck <mwilck@xxxxxxxx>
Modify the file descriptors atomically usign dup2(), and make
sure to cleanup properly even in case of an error, and to not
close stdout/in/err if the program had been started with any of
them closed.
Reviewed-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
multipathd/main.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/multipathd/main.c b/multipathd/main.c
index 36cc76f..7a57a79 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -3337,11 +3337,18 @@ failed:
return sd_notify_exit(exit_code);
}
+static void cleanup_close(int *pfd)
+{
+ if (*pfd != -1 && *pfd != STDIN_FILENO && *pfd != STDOUT_FILENO &&
+ *pfd != STDERR_FILENO)
+ close(*pfd);
+}
+
static int
daemonize(void)
{
int pid;
- int dev_null_fd;
+ int dev_null_fd __attribute__((cleanup(cleanup_close))) = -1;
if( (pid = fork()) < 0){
fprintf(stderr, "Failed first fork : %s\n", strerror(errno));
@@ -3367,25 +3374,21 @@ daemonize(void)
_exit(0);
}
- close(STDIN_FILENO);
- if (dup(dev_null_fd) < 0) {
- fprintf(stderr, "cannot dup /dev/null to stdin : %s\n",
+ if (dup2(dev_null_fd, STDIN_FILENO) < 0) {
+ fprintf(stderr, "cannot dup2 /dev/null to stdin : %s\n",
strerror(errno));
_exit(0);
}
- close(STDOUT_FILENO);
- if (dup(dev_null_fd) < 0) {
- fprintf(stderr, "cannot dup /dev/null to stdout : %s\n",
+ if (dup2(dev_null_fd, STDOUT_FILENO) < 0) {
+ fprintf(stderr, "cannot dup2 /dev/null to stdout : %s\n",
strerror(errno));
_exit(0);
}
- close(STDERR_FILENO);
- if (dup(dev_null_fd) < 0) {
+ if (dup2(dev_null_fd, STDERR_FILENO) < 0) {
fprintf(stderr, "cannot dup /dev/null to stderr : %s\n",
strerror(errno));
_exit(0);
}
- close(dev_null_fd);
daemon_pid = getpid();
return 0;
}
--
2.33.1
--
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