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>
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 1f7ea67..86a80b3 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -428,7 +428,7 @@
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 @@
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 @@
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;