iovec: make sure the caller actually wants anything in memcpy_fromiovecend

[ Upstream commit 06ebb06d49486676272a3c030bfeef4bd969a8e6 ]

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@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/core/iovec.c b/net/core/iovec.c
index a9c46ba..26dc006 100644 (file)
--- 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;