[PATCH 3.11 136/137] iovec: make sure the caller actually wants anything in memcpy_fromiovecend

[Luis Henriques]

3.11.10.15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sasha Levin <sasha.levin at oracle.com>

commit 06ebb06d49486676272a3c030bfeef4bd969a8e6 upstream.

Check for cases when the caller requests 0 bytes instead of running off
and dereferencing potentially invalid iovecs.

Signed-off-by: Sasha Levin <sasha.levin at oracle.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.11: file rename: lib/iovec.c -> net/core/iovec.c ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/core/iovec.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/iovec.c b/net/core/iovec.c
index 2145b7150beb..1117a26a8548 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -107,6 +107,10 @@ EXPORT_SYMBOL(memcpy_toiovecend);
 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 			int offset, int len)
 {
+	/* No data? Done! */
+	if (len == 0)
+		return 0;
+
 	/* Skip over the finished iovecs */
 	while (offset >= iov->iov_len) {
 		offset -= iov->iov_len;
-- 
1.9.1