SUNRPC: Properly set the @subbuf parameter of xdr_buf_subsegment()

@subbuf is an output parameter of xdr_buf_subsegment(). A survey of
call sites shows that @subbuf is always uninitialized before
xdr_buf_segment() is invoked by callers.

There are some execution paths through xdr_buf_subsegment() that do
not set all of the fields in @subbuf, leaving some pointer fields
containing garbage addresses. Subsequent processing of that buffer
then results in a page fault.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 6f7d82f..be11d67 100644 (file)
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1118,6 +1118,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
                base = 0;
        } else {
                base -= buf->head[0].iov_len;
+               subbuf->head[0].iov_base = buf->head[0].iov_base;
                subbuf->head[0].iov_len = 0;
        }
 
@@ -1130,6 +1131,8 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
                base = 0;
        } else {
                base -= buf->page_len;
+               subbuf->pages = buf->pages;
+               subbuf->page_base = 0;
                subbuf->page_len = 0;
        }
 
@@ -1141,6 +1144,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
                base = 0;
        } else {
                base -= buf->tail[0].iov_len;
+               subbuf->tail[0].iov_base = buf->tail[0].iov_base;
                subbuf->tail[0].iov_len = 0;
        }