udev: always close lock file descriptor

https://bugs.freedesktop.org/show_bug.cgi?id=79576

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

3 files changed, 30 insertions, 6 deletions

diff --git a/src/libudev/util.c b/src/libudev/util.c
index 4796505a5c..cfdf848cce 100644
--- a/src/libudev/util.c
+++ b/src/libudev/util.c
@@ -154,6 +154,30 @@ void close_nointr_nofail(int fd) {
         assert_se(close_nointr(fd) == 0);
 }
 
+int safe_close(int fd) {
+
+        /*
+         * Like close_nointr() but cannot fail. Guarantees errno is
+         * unchanged. Is a NOP with negative fds passed, and returns
+         * -1, so that it can be used in this syntax:
+         *
+         * fd = safe_close(fd);
+         */
+
+        if (fd >= 0) {
+                PROTECT_ERRNO;
+
+                /* The kernel might return pretty much any error code
+                 * via close(), but the fd will be closed anyway. The
+                 * only condition we want to check for here is whether
+                 * the fd was invalid at all... */
+
+                assert_se(close_nointr(fd) != -EBADF);
+        }
+
+        return -1;
+}
+
 int unlink_noerrno(const char *path) {
         PROTECT_ERRNO;
         int r;
diff --git a/src/libudev/util.h b/src/libudev/util.h
index a950f2658f..332dfb6207 100644
--- a/src/libudev/util.h
+++ b/src/libudev/util.h
@@ -124,6 +124,8 @@ static inline const char *startswith(const char *s, const char *prefix) {
 char *endswith(const char *s, const char *postfix) _pure_;
 
 int close_nointr(int fd);
+int safe_close(int fd);
+
 void close_nointr_nofail(int fd);
 
 int safe_atou(const char *s, unsigned *ret_u);
diff --git a/src/udev/udevd.c b/src/udev/udevd.c
index bcbb5d4d2c..b05907edb1 100644
--- a/src/udev/udevd.c
+++ b/src/udev/udevd.c
@@ -301,6 +301,7 @@ static void worker_new(struct event *event)
                                         if (fd_lock >= 0 && flock(fd_lock, LOCK_SH|LOCK_NB) < 0) {
                                                 log_debug("Unable to flock(%s), skipping event handling: %m", udev_device_get_devnode(d));
                                                 err = -EWOULDBLOCK;
+                                                fd_lock = safe_close(fd_lock);
                                                 goto skip;
                                         }
                                 }
@@ -317,8 +318,7 @@ static void worker_new(struct event *event)
                                 udev_device_update_db(dev);
                         }
 
-                        if (fd_lock >= 0)
-                                close(fd_lock);
+                        safe_close(fd_lock);
 
                         /* send processed event back to libudev listeners */
                         udev_monitor_send_device(worker_monitor, NULL, dev);
@@ -377,10 +377,8 @@ skip:
                 }
 out:
                 udev_device_unref(dev);
-                if (fd_signal >= 0)
-                        close(fd_signal);
-                if (fd_ep >= 0)
-                        close(fd_ep);
+                safe_close(fd_signal);
+                safe_close(fd_ep);
                 close(fd_inotify);
                 close(worker_watch[WRITE_END]);
                 udev_rules_unref(rules);