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>

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 3bf8a9d7f217..d7a3be5ab777 100644
--- 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;