FAILED: patch "[PATCH] sg_start_req(): make sure that there's not too many elements" failed to apply to 3.19-stable tree

The patch below does not apply to the 3.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Al Viro <[email protected]>
Date: Sat, 21 Mar 2015 20:08:18 -0400
Subject: [PATCH] sg_start_req(): make sure that there's not too many elements
in iovec

unfortunately, allowing an arbitrary 16bit value means a possibility of overflow in the calculation of total number of pages in bio_map_user_iov() - we rely on there being no more than PAGE_SIZE members of sum in the first loop there. If that sum wraps around, we end up allocating too small array of pointers to pages and it's easy to overflow it in the second loop.

X-Coverup: TINC (and there's no lumber cartel either)

index d383f84869aa..b5a4db883223 100644
@@ -1744,6 +1744,9 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
 			md->from_user = 0;
 	}
 
+	if (unlikely(iov_count > MAX_UIOVEC))
+		return -EINVAL;
+
 	if (iov_count) {
 		int size = sizeof(struct iovec) * iov_count;
 		struct iovec *iov;