[PATCH] nfsd: use xdr_encode_opaque_fixed for all GETXATTR fragments

[Aldo Ariel Panzardo]

nfsd4_vbuf_to_stream() already uses xdr_encode_opaque_fixed() when the
final fragment is shorter than a page, but the preceding memcpy() in the
loop body does not clear XDR padding.

When the last fragment happens to be exactly PAGE_SIZE the short-fragment
branch is never entered, and the loop exits through the normal buflen
path.  If that final page-sized reservation is not word-aligned within
the XDR stream, its padding bytes are left stale.

Convert the loop memcpy to xdr_encode_opaque_fixed() and drop the now
redundant short-fragment padding block, matching the first-fragment fix.

Suggested-by: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@xxxxxxxxx>
---
 fs/nfsd/nfs4xdr.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index XXXXXXX..XXXXXXX 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -5963,15 +5963,7 @@ nfsd4_vbuf_to_stream(struct xdr_stream *xdr, char *buf, u32 buflen)
 		if (!p)
 			return nfserr_resource;

-		memcpy(p, buf, cplen);
-
-		if (cplen < PAGE_SIZE) {
-			/*
-			 * We're done, with a length that wasn't page
-			 * aligned, so possibly not word aligned. Pad
-			 * any trailing bytes with 0.
-			 */
-			xdr_encode_opaque_fixed(p, NULL, cplen);
-			break;
-		}
+		xdr_encode_opaque_fixed(p, buf, cplen);
+		if (cplen < PAGE_SIZE)
+			break;

 		buflen -= PAGE_SIZE;
 		buf += PAGE_SIZE;

--
2.43.0