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NFS: clean up short packet handling for NFSv2 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 nfs_xdr_readdirres().

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Jeff Layton 2008-02-22 14:49:59 -05:00 committed by Trond Myklebust
parent 4af68bffac
commit caa02bd540
1 changed files with 28 additions and 9 deletions
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37
fs/nfs/nfs2xdr.c
View File

@ -428,7 +428,7 @@ nfs_xdr_readdirres(struct rpc_rqst *req, __be32 *p, void *dummy)
size_t hdrlen;
unsigned int pglen, recvd;
u32 len;
int status, nr;
int status, nr = 0;
__be32 *end, *entry, *kaddr;
if ((status = ntohl(*p++)))
@ -452,7 +452,12 @@ nfs_xdr_readdirres(struct rpc_rqst *req, __be32 *p, void *dummy)
kaddr = p = kmap_atomic(*page, KM_USER0);
end = (__be32 *)((char *)p + pglen);
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 + 2 > end)
goto short_pkt;
p++; /* fileid */
@ -467,18 +472,32 @@ nfs_xdr_readdirres(struct rpc_rqst *req, __be32 *p, void *dummy)
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 nr;
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) {
dprintk("NFS: readdir reply truncated!\n");
entry[1] = 1;
}
if (!nr)
nr = -errno_NFSERR_IO;
goto out;
err_unmap:
nr = -errno_NFSERR_IO;