[PATCH 5.18 022/102] SUNRPC: Fix READ_PLUS crasher

Greg Kroah-Hartman
2022-07-05T12:31:11Z

From: Chuck Lever <chuck.lever@oracle.com>

commit a23dd544debcda4ee4a549ec7de59e85c3c8345c upstream.

Looks like there are still cases when "space_left - frag1bytes" can
legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
within the current encode buffer.

Reported-by: Bruce Fields <bfields@fieldses.org>
Reported-by: Zorro Lang <zlang@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sunrpc/xdr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -979,7 +979,7 @@ static __be32 *xdr_get_next_encode_buffe
*/
xdr->p = (void *)p + frag2bytes;
space_left = xdr->buf->buflen - xdr->buf->len;
- if (space_left - nbytes >= PAGE_SIZE)
+ if (space_left - frag1bytes >= PAGE_SIZE)
xdr->end = (void *)p + PAGE_SIZE;
else
xdr->end = (void *)p + space_left - frag1bytes;