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NFS: Fix listxattr receive buffer size

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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@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2020-10-31 12:44:25 -04:00 committed by Anna Schumaker
parent 70438afbf1
commit 6c2190b3fc
1 changed files with 2 additions and 2 deletions
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4
fs/nfs/nfs42xdr.c
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@ -196,7 +196,7 @@
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 + \
@ -531,7 +531,7 @@ 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))