[CRIU] [PATCH] mount: skip '/' only if it is there

[Andrei Vagin]

From: Andrei Vagin <avagin at virtuozzo.com>

If p->mountpoint is "/", off will be 0 and we will
try to acess path[-1].

 On Tue, Sep 20, 2016 at 05:17:27PM +0300, Kirill Tkhai wrote:
>
> int off = 0;
>
> ...
>
> if (p->mountpoint[1] != 0) /* not / */
>    off = snprintf(path, len, %s, p->mountpoint);
> if (path[off - 1] == '/') /* p->mountpoint = ./ */
>
>          ^^^
> The above looks like off-by-one when off == 0. Is there is
> a condition which guarantees that off is not zero?

Reported-by: Kirill Tkhai <ktkhai at virtuozzo.com>
Cc: Kirill Tkhai <ktkhai at virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
---
 criu/path.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/criu/path.c b/criu/path.c
index c43b5e2..57773d5 100644
--- a/criu/path.c
+++ b/criu/path.c
@@ -72,10 +72,11 @@ char *mnt_get_sibling_path(struct mount_info *m,
 	cut_root = cut_root_for_bind(pa->root, p->root);
 	if (cut_root == NULL)
 		return NULL;
-	if (p->mountpoint[1] != 0) /* not "/" */
+	if (p->mountpoint[1] != 0) /* not "/" */ {
 		off = snprintf(path, len, "%s", p->mountpoint);
-	if (path[off - 1] == '/') /* p->mountpoint = "./" */
-		off--;
+		if (path[off - 1] == '/') /* p->mountpoint = "./" */
+			off--;
+	}
 	len -= off;
 	path += off;
 
-- 
2.7.4