1 files changed, 6 insertions, 4 deletions

diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
index 79d964aa8079..bf913201a6ad 100644
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -280,6 +280,7 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
                                         struct nfsd_writeargs *args)
 {
         unsigned int len, hdr, dlen;
+        struct kvec *head = rqstp->rq_arg.head;
         int v;
 
         p = decode_fh(p, &args->fh);
@@ -300,9 +301,10 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
          * Check to make sure that we got the right number of
          * bytes.
          */
-        hdr = (void*)p - rqstp->rq_arg.head[0].iov_base;
-        dlen = rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len
-                - hdr;
+        hdr = (void*)p - head->iov_base;
+        if (hdr > head->iov_len)
+                return 0;
+        dlen = head->iov_len + rqstp->rq_arg.page_len - hdr;
 
         /*
          * Round the length of the data which was specified up to
@@ -316,7 +318,7 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
                 return 0;
 
         rqstp->rq_vec[0].iov_base = (void*)p;
-        rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - hdr;
+        rqstp->rq_vec[0].iov_len = head->iov_len - hdr;
         v = 0;
         while (len > rqstp->rq_vec[v].iov_len) {
                 len -= rqstp->rq_vec[v].iov_len;