From: Chuck Lever <chuck.lever@xxxxxxxxxx> [ Upstream commit 6c2190b3fcbc92cb79e39cc7e7531656b341e463 ] Certain NFSv4.2/RDMA tests fail with v5.9-rc1. rpcrdma_convert_kvec() runs off the end of the rl_segments array because rq_rcv_buf.tail[0].iov_len holds a very large positive value. The resultant kernel memory corruption is enough to crash the client system. Callers of rpc_prepare_reply_pages() must reserve an extra XDR_UNIT in the maximum decode size for a possible XDR pad of the contents of the xdr_buf's pages. That guarantees the allocated receive buffer will be large enough to accommodate the usual contents plus that XDR pad word. encode_op_hdr() cannot add that extra word. If it does, xdr_inline_pages() underruns the length of the tail iovec. Fixes: 3e1f02123fba ("NFSv4.2: add client side XDR handling for extended attributes") Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/nfs/nfs42xdr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c index cc50085e151c5..d0ddf90c9be48 100644 --- a/fs/nfs/nfs42xdr.c +++ b/fs/nfs/nfs42xdr.c @@ -179,7 +179,7 @@ 1 + nfs4_xattr_name_maxsz + 1) #define decode_setxattr_maxsz (op_decode_hdr_maxsz + decode_change_info_maxsz) #define encode_listxattrs_maxsz (op_encode_hdr_maxsz + 2 + 1) -#define decode_listxattrs_maxsz (op_decode_hdr_maxsz + 2 + 1 + 1) +#define decode_listxattrs_maxsz (op_decode_hdr_maxsz + 2 + 1 + 1 + 1) #define encode_removexattr_maxsz (op_encode_hdr_maxsz + 1 + \ nfs4_xattr_name_maxsz) #define decode_removexattr_maxsz (op_decode_hdr_maxsz + \ @@ -504,7 +504,7 @@ static void encode_listxattrs(struct xdr_stream *xdr, { __be32 *p; - encode_op_hdr(xdr, OP_LISTXATTRS, decode_listxattrs_maxsz + 1, hdr); + encode_op_hdr(xdr, OP_LISTXATTRS, decode_listxattrs_maxsz, hdr); p = reserve_space(xdr, 12); if (unlikely(!p)) -- 2.27.0