From 3f9f8de4de49135476644297585bd910b14d0ea7 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Thu, 18 Aug 2005 13:07:15 +0200 Subject: bring std(in|out|err) fd's in a sane state If the kernel forks us as an usermodhelper, we don't have any of the standard fd's and the first open() will start with fd=0. This is inherited to all forked childs and confuses later forked helpers where we want to read from a pipe connected to the helpers stdout/stderr. # ls -l /proc/$(pidof udevd)/fd total 6 dr-x------ 2 root root 0 2005-08-18 12:44 . dr-xr-xr-x 4 root root 0 2005-08-18 12:44 .. lrwx------ 1 root root 64 2005-08-18 12:44 0 -> /dev/null lrwx------ 1 root root 64 2005-08-18 12:44 1 -> socket:[1274617] lr-x------ 1 root root 64 2005-08-18 12:44 2 -> pipe:[1274618] l-wx------ 1 root root 64 2005-08-18 12:44 3 -> pipe:[1274618] lrwx------ 1 root root 64 2005-08-18 12:44 4 -> socket:[1274619] lrwx------ 1 root root 64 2005-08-18 12:44 5 -> socket:[1274620] Ouch! This will obviously not redirect sterr, it will kill the pipe we established between the parent and the child: devnull = open("/dev/null", O_RDWR); dup2(devnull, STDERR_FILENO); Signed-off-by: Kay Sievers --- udev.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'udev.c') diff --git a/udev.c b/udev.c index beaa191c..926c4b52 100644 --- a/udev.c +++ b/udev.c @@ -72,6 +72,7 @@ int main(int argc, char *argv[], char *envp[]) const char *devpath; const char *subsystem; struct sigaction act; + int devnull; int retval = -EINVAL; if (argc == 2 && strcmp(argv[1], "-V") == 0) { @@ -79,7 +80,22 @@ int main(int argc, char *argv[], char *envp[]) exit(0); } + /* set std fd's to /dev/null, if the kernel forks us, we don't have them at all */ + devnull = open("/dev/null", O_RDWR); + if (devnull >= 0) { + if (devnull != STDIN_FILENO) + dup2(devnull, STDIN_FILENO); + if (devnull != STDOUT_FILENO) + dup2(devnull, STDOUT_FILENO); + if (devnull != STDERR_FILENO) + dup2(devnull, STDERR_FILENO); + if (devnull > STDERR_FILENO) + close(devnull); + } + logging_init("udev"); + if (devnull < 0) + err("fatal, could not open /dev/null"); udev_init_config(); dbg("version %s", UDEV_VERSION); -- cgit 1.2.3-korg