nfsd4: fix oops on unusual readlike compound

commit d5f50b0c290431c65377c4afa1c764e2c3fe5305 upstream.

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.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 87a1746..800c215 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2909,11 +2909,16 @@ 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;
        }
@@ -2959,6 +2964,8 @@ 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++]);
 
@@ -3008,6 +3015,8 @@ 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(8);  /* verifier */
        savep = p;