X-Git-Url: https://git.tokkee.org/?a=blobdiff_plain;f=lockfile.c;h=9a1f64d8d71d13ee6be48c539d79764066288f07;hb=4a21d13db4acb112bf210ab6febeed3269b28483;hp=23db35aff21d7c33197726128e2f120291e6e9f0;hpb=679c7c56ed9f73db5892fe17ef9b67b84b0ca242;p=git.git

diff --git a/lockfile.c b/lockfile.c
index 23db35aff..9a1f64d8d 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -25,22 +25,123 @@ static void remove_lock_file_on_signal(int signo)
 	raise(signo);
 }
 
+/*
+ * p = absolute or relative path name
+ *
+ * Return a pointer into p showing the beginning of the last path name
+ * element.  If p is empty or the root directory ("/"), just return p.
+ */
+static char *last_path_elm(char *p)
+{
+	/* r starts pointing to null at the end of the string */
+	char *r = strchr(p, '\0');
+
+	if (r == p)
+		return p; /* just return empty string */
+
+	r--; /* back up to last non-null character */
+
+	/* back up past trailing slashes, if any */
+	while (r > p && *r == '/')
+		r--;
+
+	/*
+	 * then go backwards until I hit a slash, or the beginning of
+	 * the string
+	 */
+	while (r > p && *(r-1) != '/')
+		r--;
+	return r;
+}
+
+
+/* We allow "recursive" symbolic links. Only within reason, though */
+#define MAXDEPTH 5
+
+/*
+ * p = path that may be a symlink
+ * s = full size of p
+ *
+ * If p is a symlink, attempt to overwrite p with a path to the real
+ * file or directory (which may or may not exist), following a chain of
+ * symlinks if necessary.  Otherwise, leave p unmodified.
+ *
+ * This is a best-effort routine.  If an error occurs, p will either be
+ * left unmodified or will name a different symlink in a symlink chain
+ * that started with p's initial contents.
+ *
+ * Always returns p.
+ */
+
+static char *resolve_symlink(char *p, size_t s)
+{
+	int depth = MAXDEPTH;
+
+	while (depth--) {
+		char link[PATH_MAX];
+		int link_len = readlink(p, link, sizeof(link));
+		if (link_len < 0) {
+			/* not a symlink anymore */
+			return p;
+		}
+		else if (link_len < sizeof(link))
+			/* readlink() never null-terminates */
+			link[link_len] = '\0';
+		else {
+			warning("%s: symlink too long", p);
+			return p;
+		}
+
+		if (link[0] == '/') {
+			/* absolute path simply replaces p */
+			if (link_len < s)
+				strcpy(p, link);
+			else {
+				warning("%s: symlink too long", p);
+				return p;
+			}
+		} else {
+			/*
+			 * link is a relative path, so I must replace the
+			 * last element of p with it.
+			 */
+			char *r = (char*)last_path_elm(p);
+			if (r - p + link_len < s)
+				strcpy(r, link);
+			else {
+				warning("%s: symlink too long", p);
+				return p;
+			}
+		}
+	}
+	return p;
+}
+
+
 static int lock_file(struct lock_file *lk, const char *path)
 {
 	int fd;
-	sprintf(lk->filename, "%s.lock", path);
+
+	if (strlen(path) >= sizeof(lk->filename)) return -1;
+	strcpy(lk->filename, path);
+	/*
+	 * subtract 5 from size to make sure there's room for adding
+	 * ".lock" for the lock file name
+	 */
+	resolve_symlink(lk->filename, sizeof(lk->filename)-5);
+	strcat(lk->filename, ".lock");
 	fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
 	if (0 <= fd) {
+		if (!lock_file_list) {
+			signal(SIGINT, remove_lock_file_on_signal);
+			atexit(remove_lock_file);
+		}
 		lk->owner = getpid();
 		if (!lk->on_list) {
 			lk->next = lock_file_list;
 			lock_file_list = lk;
 			lk->on_list = 1;
 		}
-		if (lock_file_list) {
-			signal(SIGINT, remove_lock_file_on_signal);
-			atexit(remove_lock_file);
-		}
 		if (adjust_shared_perm(lk->filename))
 			return error("cannot fix permission bits on %s",
 				     lk->filename);
@@ -97,4 +198,3 @@ void rollback_lock_file(struct lock_file *lk)
 		unlink(lk->filename);
 	lk->filename[0] = 0;
 }
-