From 5c37a8a720a39c881fe8e5ee59de1e570f9ce01d Mon Sep 17 00:00:00 2001
From: Alan Coopersmith <alan.coopersmith@oracle.com>
Date: Wed, 22 Jan 2014 23:12:04 -0800
Subject: [PATCH 07/33] dbe: unvalidated lengths in DbeSwapBuffers calls
 [CVE-2014-8097]

ProcDbeSwapBuffers() has a 32bit (n) length value that it uses to read
from a buffer. The length is never validated, which can lead to out of
bound reads, and possibly returning the data read from out of bounds to
the misbehaving client via an X Error packet.

SProcDbeSwapBuffers() swaps data (for correct endianness) before
handing it off to the real proc.  While doing the swapping, the
length field is not validated, which can cause memory corruption.

v2: reorder checks to avoid compilers optimizing out checks for overflow
that happen after we'd already have done the overflowing multiplications.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Fedora X Ninjas <x@fedoraproject.org>
---
 dbe/dbe.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/dbe/dbe.c b/dbe/dbe.c
index 8d8bfb9..9be5297 100644
--- a/dbe/dbe.c
+++ b/dbe/dbe.c
@@ -450,18 +450,20 @@ ProcDbeSwapBuffers(ClientPtr client)
     DbeSwapInfoPtr swapInfo;
     xDbeSwapInfo *dbeSwapInfo;
     int error;
-    register int i, j;
-    int nStuff;
+    unsigned int i, j;
+    unsigned int nStuff;
 
     REQUEST_AT_LEAST_SIZE(xDbeSwapBuffersReq);
     nStuff = stuff->n;          /* use local variable for performance. */
 
     if (nStuff == 0) {
+        REQUEST_SIZE_MATCH(xDbeSwapBuffersReq);
         return Success;
     }
 
     if (nStuff > UINT32_MAX / sizeof(DbeSwapInfoRec))
         return BadAlloc;
+    REQUEST_FIXED_SIZE(xDbeSwapBuffersReq, nStuff * sizeof(xDbeSwapInfo));
 
     /* Get to the swap info appended to the end of the request. */
     dbeSwapInfo = (xDbeSwapInfo *) & stuff[1];
@@ -914,13 +916,16 @@ static int
 SProcDbeSwapBuffers(ClientPtr client)
 {
     REQUEST(xDbeSwapBuffersReq);
-    register int i;
+    unsigned int i;
     xDbeSwapInfo *pSwapInfo;
 
     swaps(&stuff->length);
     REQUEST_AT_LEAST_SIZE(xDbeSwapBuffersReq);
 
     swapl(&stuff->n);
+    if (stuff->n > UINT32_MAX / sizeof(DbeSwapInfoRec))
+        return BadAlloc;
+    REQUEST_FIXED_SIZE(xDbeSwapBuffersReq, stuff->n * sizeof(xDbeSwapInfo));
 
     if (stuff->n != 0) {
         pSwapInfo = (xDbeSwapInfo *) stuff + 1;
-- 
1.9.3