Commit 7bda2cdf authored by Jeff Layton's avatar Jeff Layton Committed by Trond Myklebust
Browse files

NFS: clean up short packet handling for NFSv4 readdir 



Currently, the NFS readdir decoders have a workaround for buggy servers
that send an empty readdir response with the EOF bit unset. If the
server sends a malformed response in some cases, this workaround kicks
in and just returns an empty response rather than returning a proper
error to the caller.

This patch does 3 things:

1) have malformed responses with no entries return error (-EIO)

2) preserve existing workaround for servers that send empty
   responses with the EOF marker unset.

3) Add some comments to clarify the logic in decode_readdir().

Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 643f8111

fs/nfs/nfs4xdr.c

+27 −10
Original line number Diff line number Diff line
@@ -3481,7 +3481,7 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n 
	size_t		hdrlen;

	u32		recvd, pglen = rcvbuf->page_len;

	__be32		*end, *entry, *p, *kaddr;

	unsigned int	nr;

	unsigned int	nr = 0;

	int		status;



	status = decode_op_hdr(xdr, OP_READDIR);
@@ -3505,7 +3505,12 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n 
	kaddr = p = kmap_atomic(page, KM_USER0);

	end = p + ((pglen + readdir->pgbase) >> 2);

	entry = p;

	for (nr = 0; *p++; nr++) {



	/* Make sure the packet actually has a value_follows and EOF entry */

	if ((entry + 1) > end)

		goto short_pkt;



	for (; *p++; nr++) {

		u32 len, attrlen, xlen;

		if (end - p < 3)

			goto short_pkt;
@@ -3532,19 +3537,31 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n 
		p += attrlen;		/* attributes */

		entry = p;

	}

	if (!nr && (entry[0] != 0 || entry[1] == 0))

		goto short_pkt;

	/*

	 * Apparently some server sends responses that are a valid size, but

	 * contain no entries, and have value_follows==0 and EOF==0. For

	 * those, just set the EOF marker.

	 */

	if (!nr && entry[1] == 0) {

		dprintk("NFS: readdir reply truncated!\n");

		entry[1] = 1;

	}

out:	

	kunmap_atomic(kaddr, KM_USER0);

	return 0;

short_pkt:

	/*

	 * When we get a short packet there are 2 possibilities. We can

	 * return an error, or fix up the response to look like a valid

	 * response and return what we have so far. If there are no

	 * entries and the packet was short, then return -EIO. If there

	 * are valid entries in the response, return them and pretend that

	 * the call was successful, but incomplete. The caller can retry the

	 * readdir starting at the last cookie.

	 */

	dprintk("%s: short packet at entry %d\n", __FUNCTION__, nr);

	entry[0] = entry[1] = 0;

	/* truncate listing ? */

	if (!nr) {

		dprintk("NFS: readdir reply truncated!\n");

		entry[1] = 1;

	}

	if (nr)

		goto out;

err_unmap:

	kunmap_atomic(kaddr, KM_USER0);

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