iovec: make sure the caller actually wants anything in memcpy_fromiovecend

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>

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/iovec.c b/lib/iovec.c
index 7a7c2da4cddf..df3abd1eaa4a 100644
--- a/lib/iovec.c
+++ b/lib/iovec.c
@@ -85,6 +85,10 @@ 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;