Merge pull request #24691 from yuwata/udev-node-check-existence

udev: check existence of device node

1 files changed, 78 insertions, 55 deletions

diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c
index 4e7dca06de..f3da48862b 100644
--- a/src/udev/udev-node.c
+++ b/src/udev/udev-node.c
@@ -122,6 +122,78 @@ static int node_symlink(sd_device *dev, const char *devnode, const char *slink)
         return 0;
 }
 
+static int stack_directory_read_one(int dirfd, const char *id, bool is_symlink, char **devnode, int *priority) {
+        int tmp_prio, r;
+
+        assert(dirfd >= 0);
+        assert(id);
+        assert(devnode);
+        assert(priority);
+
+        if (is_symlink) {
+                _cleanup_free_ char *buf = NULL;
+                char *colon;
+
+                /* New format. The devnode and priority can be obtained from symlink. */
+
+                r = readlinkat_malloc(dirfd, id, &buf);
+                if (r < 0)
+                        return r;
+
+                colon = strchr(buf, ':');
+                if (!colon || colon == buf)
+                        return -EINVAL;
+
+                *colon = '\0';
+
+                /* Of course, this check is racy, but it is not necessary to be perfect. Even if the device
+                 * node will be removed after this check, we will receive 'remove' uevent, and the invalid
+                 * symlink will be removed during processing the event. The check is just for shortening the
+                 * timespan that the symlink points to a non-existing device node. */
+                if (access(colon + 1, F_OK) < 0)
+                        return -errno;
+
+                r = safe_atoi(buf, &tmp_prio);
+                if (r < 0)
+                        return r;
+
+                if (*devnode && tmp_prio <= *priority)
+                        return 0; /* Unchanged */
+
+                r = free_and_strdup(devnode, colon + 1);
+                if (r < 0)
+                        return r;
+
+        } else {
+                _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+                const char *val;
+
+                /* Old format. The devnode and priority must be obtained from uevent and udev database. */
+
+                r = sd_device_new_from_device_id(&dev, id);
+                if (r < 0)
+                        return r;
+
+                r = device_get_devlink_priority(dev, &tmp_prio);
+                if (r < 0)
+                        return r;
+
+                if (*devnode && tmp_prio <= *priority)
+                        return 0; /* Unchanged */
+
+                r = sd_device_get_devname(dev, &val);
+                if (r < 0)
+                        return r;
+
+                r = free_and_strdup(devnode, val);
+                if (r < 0)
+                        return r;
+        }
+
+        *priority = tmp_prio;
+        return 1; /* Updated */
+}
+
 static int stack_directory_find_prioritized_devnode(sd_device *dev, const char *dirname, bool add, char **ret) {
         _cleanup_closedir_ DIR *dir = NULL;
         _cleanup_free_ char *devnode = NULL;
@@ -160,8 +232,6 @@ static int stack_directory_find_prioritized_devnode(sd_device *dev, const char *
                 return r;
 
         FOREACH_DIRENT_ALL(de, dir, break) {
-                int tmp_prio;
-
                 if (de->d_name[0] == '.')
                         continue;
 
@@ -169,61 +239,14 @@ static int stack_directory_find_prioritized_devnode(sd_device *dev, const char *
                 if (streq(de->d_name, id))
                         continue;
 
-                if (de->d_type == DT_LNK) {
-                        _cleanup_free_ char *buf = NULL;
-                        char *colon;
-
-                        /* New format. The devnode and priority can be obtained from symlink. */
-
-                        r = readlinkat_malloc(dirfd(dir), de->d_name, &buf);
-                        if (r < 0) {
-                                log_device_debug_errno(dev, r, "Failed to read symlink %s, ignoring: %m", de->d_name);
-                                continue;
-                        }
-
-                        colon = strchr(buf, ':');
-                        if (!colon || colon == buf)
-                                continue;
-
-                        *colon = '\0';
-
-                        if (safe_atoi(buf, &tmp_prio) < 0)
-                                continue;
-
-                        if (devnode && tmp_prio <= priority)
-                                continue;
-
-                        r = free_and_strdup(&devnode, colon + 1);
-                        if (r < 0)
-                                return r;
-
-                } else if (de->d_type == DT_REG) {
-                        _cleanup_(sd_device_unrefp) sd_device *tmp_dev = NULL;
-                        const char *val;
-
-                        /* Old format. The devnode and priority must be obtained from uevent and
-                         * udev database files. */
-
-                        if (sd_device_new_from_device_id(&tmp_dev, de->d_name) < 0)
-                                continue;
-
-                        if (device_get_devlink_priority(tmp_dev, &tmp_prio) < 0)
-                                continue;
-
-                        if (devnode && tmp_prio <= priority)
-                                continue;
-
-                        if (sd_device_get_devname(tmp_dev, &val) < 0)
-                                continue;
-
-                        r = free_and_strdup(&devnode, val);
-                        if (r < 0)
-                                return r;
-
-                } else
+                if (!IN_SET(de->d_type, DT_LNK, DT_REG))
                         continue;
 
-                priority = tmp_prio;
+                r = stack_directory_read_one(dirfd(dir), de->d_name, /* is_symlink = */ de->d_type == DT_LNK, &devnode, &priority);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to read '%s/%s', ignoring: %m", dirname, de->d_name);
+                        continue;
+                }
         }
 
         *ret = TAKE_PTR(devnode);