lxc.rootfs: support multiple lower layers

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@mailbox.org> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

lxc.rootfs: support multiple lower layers
9208af16 · Christian Brauner · Stéphane Graber · f267d666 · 9208af16
Commit 9208af16 authored Jan 20, 2016 by Christian Brauner Committed by Stéphane Graber Jan 28, 2016
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Showing with 10 additions and 4 deletions

lxcoverlay.c src/lxc/bdev/lxcoverlay.c +10 -4

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--- 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++;