Attachment 303356 Details for Bug 443655 – clean up short packet handling for NFSv4 readdir

[patch] clean up short packet handling for NFSv4 readdir

09-bz-428720-nfs-clean-up-short-p.patch (text/plain), 3.03 KB, created by Jeff Layton on 2008-04-22 18:31:03 UTC

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Creator: Jeff Layton

Created: 2008-04-22 18:31:03 UTC

Size: 3.03 KB

patch

obsolete

>BZ#428720: NFS: clean up short packet handling for NFSv4 readdir
>
>From: Jeff Layton <jlayton@redhat.com>
>
>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: Jeff Layton <jlayton@redhat.com>
>---
>
> fs/nfs/nfs4xdr.c |   37 +++++++++++++++++++++++++++----------
> 1 files changed, 27 insertions(+), 10 deletions(-)
>
>
>diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>index e118ce1..b3d3121 100644
>--- a/fs/nfs/nfs4xdr.c
>+++ b/fs/nfs/nfs4xdr.c
>@@ -3035,7 +3035,7 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
> 	struct xdr_buf	*rcvbuf = &req->rq_rcv_buf;
> 	struct page	*page = *rcvbuf->pages;
> 	struct kvec	*iov = rcvbuf->head;
>-	unsigned int	nr, pglen = rcvbuf->page_len;
>+	unsigned int	nr = 0, pglen = rcvbuf->page_len;
> 	uint32_t	*end, *entry, *p, *kaddr;
> 	uint32_t	len, attrlen;
> 	int 		hdrlen, recvd, status;
>@@ -3056,7 +3056,12 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
> 	kaddr = p = (uint32_t *) kmap_atomic(page, KM_USER0);
> 	end = (uint32_t *) ((char *)p + pglen + readdir->pgbase);
> 	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++) {
> 		if (p + 3 > end)
> 			goto short_pkt;
> 		p += 2;			/* cookie */
>@@ -3078,19 +3083,31 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
> 			goto short_pkt;
> 		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.
>+	 */
> 	entry[0] = entry[1] = 0;
>-	/* truncate listing ? */
>-	if (!nr) {
>-		printk(KERN_NOTICE "NFS: readdir reply truncated!\n");
>-		entry[1] = 1;
>-	}
>-	goto out;
>+	if (nr)
>+		goto out;
> err_unmap:
> 	kunmap_atomic(kaddr, KM_USER0);
> 	return -errno_NFSERR_IO;

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