nfsd4: fix oops on unusual readlike compound

If the argument and reply together exceed the maximum payload size, then
a reply with a read-like operation can overlow the rq_pages array.

Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 3bf8a9d7f2171e67c0ebf8507deb60ab3cb1187b..d7a3be5ab777f353e2ff41eb2ad3a5cb0b925320 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2925,11 +2925,16 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, __be32 nfserr,
        len = maxcount;
        v = 0;
        while (len > 0) {
-               pn = resp->rqstp->rq_resused++;
+               pn = resp->rqstp->rq_resused;
+               if (!resp->rqstp->rq_respages[pn]) { /* ran out of pages */
+                       maxcount -= len;
+                       break;
+               }
                resp->rqstp->rq_vec[v].iov_base =
                        page_address(resp->rqstp->rq_respages[pn]);
                resp->rqstp->rq_vec[v].iov_len =
                        len < PAGE_SIZE ? len : PAGE_SIZE;
+               resp->rqstp->rq_resused++;
                v++;
                len -= PAGE_SIZE;
        }
@@ -2975,6 +2980,8 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd
                return nfserr;
        if (resp->xbuf->page_len)
                return nfserr_resource;
+       if (!resp->rqstp->rq_respages[resp->rqstp->rq_resused])
+               return nfserr_resource;
 
        page = page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused++]);
 
@@ -3024,6 +3031,8 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4
                return nfserr;
        if (resp->xbuf->page_len)
                return nfserr_resource;
+       if (!resp->rqstp->rq_respages[resp->rqstp->rq_resused])
+               return nfserr_resource;
 
        RESERVE_SPACE(NFS4_VERIFIER_SIZE);
        savep = p;