1 files changed, 39 insertions, 7 deletions

diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
index 0c24b9e24fe8..6035e03655c6 100644
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -284,8 +284,9 @@ int
 nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
                                         struct nfsd_writeargs *args)
 {
-        unsigned int len;
+        unsigned int len, hdr, dlen;
         int v;
+
         if (!(p = decode_fh(p, &args->fh)))
                 return 0;
 
@@ -293,11 +294,42 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
         args->offset = ntohl(*p++);     /* offset */
         p++;                            /* totalcount */
         len = args->len = ntohl(*p++);
-        rqstp->rq_vec[0].iov_base = (void*)p;
-        rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len -
-                                (((void*)p) - rqstp->rq_arg.head[0].iov_base);
+        /*
+         * The protocol specifies a maximum of 8192 bytes.
+         */
         if (len > NFSSVC_MAXBLKSIZE_V2)
-                len = NFSSVC_MAXBLKSIZE_V2;
+                return 0;
+
+        /*
+         * Check to make sure that we got the right number of
+         * bytes.
+         *
+         * If more than one page was used, then compute the length
+         * of the data in the request as the total size of the
+         * request minus the transport protocol headers minus the
+         * RPC protocol headers minus the NFS protocol fields
+         * already consumed.  If the request fits into a single
+         * page, then compete the length of the data as the size
+         * of the NFS portion of the request minus the NFS
+         * protocol fields already consumed.
+         */
+        hdr = (void*)p - rqstp->rq_arg.head[0].iov_base;
+        if (rqstp->rq_respages != rqstp->rq_pages + 1) {
+                dlen = rqstp->rq_arg.len -
+                        (PAGE_SIZE - rqstp->rq_arg.head[0].iov_len) - hdr;
+        } else {
+                dlen = rqstp->rq_arg.head[0].iov_len - hdr;
+        }
+        /*
+         * Round the length of the data which was specified up to
+         * the next multiple of XDR units and then compare that
+         * against the length which was actually received.
+         */
+        if (dlen != ((len + 3) & ~0x3))
+                return 0;
+
+        rqstp->rq_vec[0].iov_base = (void*)p;
+        rqstp->rq_vec[0].iov_len = rqstp->rq_arg.head[0].iov_len - hdr;
         v = 0;
         while (len > rqstp->rq_vec[v].iov_len) {
                 len -= rqstp->rq_vec[v].iov_len;
@@ -306,8 +338,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
                 rqstp->rq_vec[v].iov_len = PAGE_SIZE;
         }
         rqstp->rq_vec[v].iov_len = len;
-        args->vlen = v+1;
-        return rqstp->rq_vec[0].iov_len > 0;
+        args->vlen = v + 1;
+        return 1;
 }
 
 int