SUNRPC: Don't decode beyond the end of the RPC reply message

Now that xdr_inline_decode() will automatically cross into the page
buffers, we need to ensure that it doesn't exceed the total reply
message length.

This patch sets up a counter that tracks the number of words
remaining in the reply message, and ensures that xdr_inline_decode,
xdr_read_pages and xdr_enter_page respect the end of message boundary.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 21 insertions, 7 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 21d041cf7f65..5643feb6c645 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -630,12 +630,15 @@ void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p)
         xdr->buf = buf;
         xdr->scratch.iov_base = NULL;
         xdr->scratch.iov_len = 0;
+        xdr->nwords = XDR_QUADLEN(buf->len);
         if (buf->head[0].iov_len != 0)
                 xdr_set_iov(xdr, buf->head, buf->len);
         else if (buf->page_len != 0)
                 xdr_set_page_base(xdr, 0, buf->len);
-        if (p != NULL && p > xdr->p && xdr->end >= p)
+        if (p != NULL && p > xdr->p && xdr->end >= p) {
+                xdr->nwords -= p - xdr->p;
                 xdr->p = p;
+        }
 }
 EXPORT_SYMBOL_GPL(xdr_init_decode);
 
@@ -660,12 +663,14 @@ EXPORT_SYMBOL_GPL(xdr_init_decode_pages);
 
 static __be32 * __xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 {
+        unsigned int nwords = XDR_QUADLEN(nbytes);
         __be32 *p = xdr->p;
-        __be32 *q = p + XDR_QUADLEN(nbytes);
+        __be32 *q = p + nwords;
 
-        if (unlikely(q > xdr->end || q < p))
+        if (unlikely(nwords > xdr->nwords || q > xdr->end || q < p))
                 return NULL;
         xdr->p = q;
+        xdr->nwords -= nwords;
         return p;
 }
 
@@ -746,9 +751,16 @@ void xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
         struct xdr_buf *buf = xdr->buf;
         struct kvec *iov;
         ssize_t shift;
+        unsigned int nwords = XDR_QUADLEN(len);
         unsigned int end;
         int padding;
 
+        if (xdr->nwords == 0)
+                return;
+        if (nwords > xdr->nwords) {
+                nwords = xdr->nwords;
+                len = nwords << 2;
+        }
         /* Realign pages to current pointer position */
         iov  = buf->head;
         shift = iov->iov_len + (char *)iov->iov_base - (char *)xdr->p;
@@ -758,15 +770,15 @@ void xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
         /* Truncate page data and move it into the tail */
         if (buf->page_len > len)
                 xdr_shrink_pagelen(buf, buf->page_len - len);
-        padding = (XDR_QUADLEN(len) << 2) - len;
+        padding = (nwords << 2) - len;
         xdr->iov = iov = buf->tail;
         /* Compute remaining message length.  */
         end = iov->iov_len;
         shift = buf->buflen - buf->len;
-        if (shift < end)
+        if (end > shift + padding)
                 end -= shift;
-        else if (shift > 0)
-                end = 0;
+        else
+                end = padding;
         /*
          * Position current pointer at beginning of tail, and
          * set remaining message length.
@@ -774,6 +786,7 @@ void xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
         xdr->p = (__be32 *)((char *)iov->iov_base + padding);
         xdr->end = (__be32 *)((char *)iov->iov_base + end);
         xdr->page_ptr = NULL;
+        xdr->nwords = XDR_QUADLEN(end - padding);
 }
 EXPORT_SYMBOL_GPL(xdr_read_pages);
 
@@ -795,6 +808,7 @@ void xdr_enter_page(struct xdr_stream *xdr, unsigned int len)
          * set remaining message length.
          */
         xdr_set_page_base(xdr, 0, len);
+        xdr->nwords += XDR_QUADLEN(xdr->buf->page_len);
 }
 EXPORT_SYMBOL_GPL(xdr_enter_page);