nfsd4: enforce rd_dircount

As long as we're here, let's enforce the protocol's limit on the number
of directory entries to return in a readdir.

I don't think anyone's ever noticed our lack of enforcement, but maybe
there's more of a chance they will now that we allow larger readdirs.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 4d79e5366a82..3f2a52ccb9d1 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1033,7 +1033,7 @@ nfsd4_decode_readdir(struct nfsd4_compoundargs *argp, struct nfsd4_readdir *read
         READ_BUF(24);
         READ64(readdir->rd_cookie);
         COPYMEM(readdir->rd_verf.data, sizeof(readdir->rd_verf.data));
-        READ32(readdir->rd_dircount);    /* just in case you needed a useless field... */
+        READ32(readdir->rd_dircount);
         READ32(readdir->rd_maxcount);
         if ((status = nfsd4_decode_bitmap(argp, readdir->rd_bmval)))
                 goto out;
@@ -2720,6 +2720,9 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
         if (entry_bytes > cd->rd_maxcount)
                 goto fail;
         cd->rd_maxcount -= entry_bytes;
+        if (!cd->rd_dircount)
+                goto fail;
+        cd->rd_dircount--;
         cd->cookie_offset = cookie_offset;
 skip_entry:
         cd->common.err = nfs_ok;