util_run_program: restore signal mask before executing event RUN commands

External programs triggered by events (via RUN=) will inherit udev's
signal mask, which is set to block all but SIGALRM. For most utilities,
this is OK, but if we start daemons from RUN=, we run into trouble
(especially as SIGCHLD is blocked).

This change saves the original sigmask when udev starts, and restores it
just before we exec() the external command.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

7 files changed, 20 insertions, 10 deletions

diff --git a/libudev/libudev-private.h b/libudev/libudev-private.h
index b735298c67..e90c79cb3e 100644
--- a/libudev/libudev-private.h
+++ b/libudev/libudev-private.h
@@ -13,6 +13,7 @@
 #define _LIBUDEV_PRIVATE_H_
 
 #include <syslog.h>
+#include <signal.h>
 #include "libudev.h"
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
@@ -214,7 +215,8 @@ int util_unlink_secure(struct udev *udev, const char *filename);
 uid_t util_lookup_user(struct udev *udev, const char *user);
 gid_t util_lookup_group(struct udev *udev, const char *group);
 int util_run_program(struct udev *udev, const char *command, char **envp,
-		     char *result, size_t ressize, size_t *reslen);
+		     char *result, size_t ressize, size_t *reslen,
+		     const sigset_t *sigmask);
 int util_resolve_subsys_kernel(struct udev *udev, const char *string,
 				      char *result, size_t maxsize, int read_value);
 
diff --git a/libudev/libudev-util-private.c b/libudev/libudev-util-private.c
index fe8f29b3a8..dfde5a998d 100644
--- a/libudev/libudev-util-private.c
+++ b/libudev/libudev-util-private.c
@@ -242,7 +242,8 @@ int util_resolve_subsys_kernel(struct udev *udev, const char *string,
 }
 
 int util_run_program(struct udev *udev, const char *command, char **envp,
-		     char *result, size_t ressize, size_t *reslen)
+		     char *result, size_t ressize, size_t *reslen,
+		     const sigset_t *sigmask)
 {
 	int status;
 	int outpipe[2] = {-1, -1};
@@ -330,6 +331,10 @@ int util_run_program(struct udev *udev, const char *command, char **envp,
 			dup2(errpipe[WRITE_END], STDERR_FILENO);
 			close(errpipe[WRITE_END]);
 		}
+
+		if (sigmask)
+			sigprocmask(SIG_BLOCK, sigmask, NULL);
+
 		execve(argv[0], argv, envp);
 		if (errno == ENOENT || errno == ENOTDIR) {
 			/* may be on a filesystem which is not mounted right now */
diff --git a/udev/test-udev.c b/udev/test-udev.c
index c6b8bf573b..0806fbf9ce 100644
--- a/udev/test-udev.c
+++ b/udev/test-udev.c
@@ -103,7 +103,7 @@ int main(int argc, char *argv[])
 		alarm(udev_device_get_event_timeout(dev));
 
 	if (err == 0 && !event->ignore_device && udev_get_run(udev))
-		udev_event_execute_run(event);
+		udev_event_execute_run(event, NULL);
 
 	udev_event_unref(event);
 	udev_device_unref(dev);
diff --git a/udev/udev-event.c b/udev/udev-event.c
index 8183793e5f..7b4e4ac5c3 100644
--- a/udev/udev-event.c
+++ b/udev/udev-event.c
@@ -722,7 +722,7 @@ exit:
 	return err;
 }
 
-int udev_event_execute_run(struct udev_event *event)
+int udev_event_execute_run(struct udev_event *event, const sigset_t *sigmask)
 {
 	struct udev_list_entry *list_entry;
 	int err = 0;
@@ -745,7 +745,7 @@ int udev_event_execute_run(struct udev_event *event)
 
 			udev_event_apply_format(event, cmd, program, sizeof(program));
 			envp = udev_device_get_properties_envp(event->dev);
-			if (util_run_program(event->udev, program, envp, NULL, 0, NULL) != 0) {
+			if (util_run_program(event->udev, program, envp, NULL, 0, NULL, sigmask) != 0) {
 				if (udev_list_entry_get_flag(list_entry))
 					err = -1;
 			}
diff --git a/udev/udev-rules.c b/udev/udev-rules.c
index a92446403f..20ec2706bd 100644
--- a/udev/udev-rules.c
+++ b/udev/udev-rules.c
@@ -749,7 +749,7 @@ static int import_program_into_properties(struct udev_device *dev, const char *p
 	char *line;
 
 	envp = udev_device_get_properties_envp(dev);
-	if (util_run_program(udev, program, envp, result, sizeof(result), &reslen) != 0)
+	if (util_run_program(udev, program, envp, result, sizeof(result), &reslen, NULL) != 0)
 		return -1;
 
 	line = result;
@@ -2206,7 +2206,7 @@ int udev_rules_apply_to_event(struct udev_rules *rules, struct udev_event *event
 				     program,
 				     &rules->buf[rule->rule.filename_off],
 				     rule->rule.filename_line);
-				if (util_run_program(event->udev, program, envp, result, sizeof(result), NULL) != 0) {
+				if (util_run_program(event->udev, program, envp, result, sizeof(result), NULL, NULL) != 0) {
 					if (cur->key.op != OP_NOMATCH)
 						goto nomatch;
 				} else {
diff --git a/udev/udev.h b/udev/udev.h
index 391276f6e4..8f0a3014b6 100644
--- a/udev/udev.h
+++ b/udev/udev.h
@@ -21,6 +21,7 @@
 
 #include <sys/types.h>
 #include <sys/param.h>
+#include <signal.h>
 
 #include "libudev.h"
 #include "libudev-private.h"
@@ -67,7 +68,7 @@ int udev_rules_apply_to_event(struct udev_rules *rules, struct udev_event *event
 struct udev_event *udev_event_new(struct udev_device *dev);
 void udev_event_unref(struct udev_event *event);
 int udev_event_execute_rules(struct udev_event *event, struct udev_rules *rules);
-int udev_event_execute_run(struct udev_event *event);
+int udev_event_execute_run(struct udev_event *event, const sigset_t *sigset);
 size_t udev_event_apply_format(struct udev_event *event, const char *src, char *dest, size_t size);
 int udev_event_apply_subsys_kernel(struct udev_event *event, const char *string,
 				   char *result, size_t maxsize, int read_value);
diff --git a/udev/udevd.c b/udev/udevd.c
index 54064cbfcf..2eb914a3f3 100644
--- a/udev/udevd.c
+++ b/udev/udevd.c
@@ -79,6 +79,7 @@ static bool stop_exec_queue;
 static bool reload_config;
 static int max_childs;
 static int childs;
+static sigset_t orig_sigmask;
 static struct udev_list_node event_list;
 static struct udev_list_node worker_list;
 static bool udev_exit;
@@ -292,7 +293,8 @@ static void worker_new(struct event *event)
 
 			/* execute RUN= */
 			if (err == 0 && !udev_event->ignore_device && udev_get_run(udev_event->udev))
-				failed = udev_event_execute_run(udev_event);
+				failed = udev_event_execute_run(udev_event,
+								&orig_sigmask);
 
 			/* reset alarm */
 			alarm(0);
@@ -926,7 +928,7 @@ int main(int argc, char *argv[])
 
 	/* block and listen to all signals on signalfd */
 	sigfillset(&mask);
-	sigprocmask(SIG_SETMASK, &mask, NULL);
+	sigprocmask(SIG_SETMASK, &mask, &orig_sigmask);
 	pfd[FD_SIGNAL].fd = signalfd(-1, &mask, 0);
 	if (pfd[FD_SIGNAL].fd < 0) {
 		fprintf(stderr, "error getting signalfd\n");