Skip calling mount(8) if /etc/mtab doesn't exist...

2 files changed, 24 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 638dd3c..4f56566 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,10 @@
 	* Fix handling of (no)suid and (no)dev options if filesystem is
 	mounted from /etc/fstab or via mount(8).  Reported by Jan Ondrej.
 
+	* Skip calling mount(8) if /etc/mtab doesn't exist or if it's on a
+	read-only filesystem.  This works around issues with certain mount
+	implementations.  Reported by Szabolcs Szakacsits.
+
 2008-06-16  Miklos Szeredi <miklos@szeredi.hu>
 
 	* Remove fuse kernel module sources.  Linux 2.6.27 will support
diff --git a/lib/mount_util.c b/lib/mount_util.c
index 7db8060..e78b482 100644
--- a/lib/mount_util.c
+++ b/lib/mount_util.c
@@ -22,6 +22,7 @@
 
 static int mtab_needs_update(const char *mnt)
 {
+	int res;
 	struct stat stbuf;
 
 	/* If mtab is within new mount, don't touch it */
@@ -29,8 +30,25 @@ static int mtab_needs_update(const char *mnt)
 	    _PATH_MOUNTED[strlen(mnt)] == '/')
 		return 0;
 
-	if (lstat(_PATH_MOUNTED, &stbuf) != -1 && S_ISLNK(stbuf.st_mode))
-		return 0;
+	/*
+	 * Skip mtab update if /etc/mtab:
+	 *
+	 *  - doesn't exist,
+	 *  - is a symlink,
+	 *  - is on a read-only filesystem.
+	 */
+	res = lstat(_PATH_MOUNTED, &stbuf);
+	if (res == -1) {
+		if (errno == ENOENT)
+			return 0;
+	} else {
+		if (S_ISLNK(stbuf.st_mode))
+			return 0;
+
+		res = access(_PATH_MOUNTED, W_OK);
+		if (res == -1 && errno == EROFS)
+			return 0;
+	}
 
 	return 1;
 }