[lxc-devel] [PATCH] lxc.rootfs: support multiple lower layers

[Christian Brauner]

Do it in a safe way by using strstr() to check for the substring ":/" should
':' be part of a pathname. This should be a safer implementation than the one
originally suggested in #547.

Signed-off-by: Christian Brauner <christian.brauner at mailbox.org>
---
 src/lxc/bdev/lxcoverlay.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/lxc/bdev/lxcoverlay.c b/src/lxc/bdev/lxcoverlay.c
index d06d24f..5ffc289 100644
--- a/src/lxc/bdev/lxcoverlay.c
+++ b/src/lxc/bdev/lxcoverlay.c
@@ -309,7 +309,7 @@ char *ovl_getlower(char *p)
 
 int ovl_mount(struct bdev *bdev)
 {
-	char *options, *dup, *lower, *upper;
+	char *tmp, *options, *dup, *lower, *upper;
 	char *options_work, *work, *lastslash;
 	int lastslashidx;
 	int len, len2;
@@ -331,9 +331,15 @@ int ovl_mount(struct bdev *bdev)
 	 */
 	dup = alloca(strlen(bdev->src) + 1);
 	strcpy(dup, bdev->src);
-	if (!(lower = strchr(dup, ':')))
-		return -22;
-	if (!(upper = strchr(++lower, ':')))
+	/* support multiple lower layers */
+	if (!(lower = strstr(dup, ":/")))
+			return -22;
+	lower++;
+	upper = lower;
+	while ((tmp = strstr(++upper, ":/"))) {
+		upper = tmp;
+	}
+	if (--upper == lower)
 		return -22;
 	*upper = '\0';
 	upper++;
-- 
2.7.0