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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/core/iovec.c b/net/core/iovec.c
index fcf9ee7..66e3f1f 100644 (file)
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -157,6 +157,10 @@ EXPORT_SYMBOL(memcpy_fromiovec);
 int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
                        int offset, int len)
 {
 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;
        /* Skip over the finished iovecs */
        while (offset >= iov->iov_len) {
                offset -= iov->iov_len;