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commit ac9fbaabd6bdbca6dd1d94fa385aea41fdebf2c1
Author: Karl Tomlinson <xmail@karlt.net>
Date: Wed Apr 15 10:16:18 2015 +0200
MakeBigReq: don't move the last word, already handled by Data32 (X.Org CVE-2013-7439).
MakeBigReq inserts a length field after the first 4 bytes of the request
(after req->length), pushing everything else back by 4 bytes.
The current memmove moves everything but the first 4 bytes back. If a
request aligns to the end of the buffer pointer when MakeBigReq is
invoked for that request, this runs over the buffer. Instead, we need to
memmove minus the first 4 bytes (which aren't moved), minus the last 4
bytes (so we still align to the previous tail).
The 4 bytes that fell out are already handled with Data32, which will
handle the buffermax correctly.
The case where req->length = 1 was already not functional.
Reported by Abhishek Arya <inferno@chromium.org> (against X.Org BTS).
https://bugzilla.mozilla.org/show_bug.cgi?id=803762
Reviewed-by: Jeff Muizelaar <jmuizelaar@mozilla.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Rebased-for-NX: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
--- a/nx-X11/lib/X11/Xlibint.h
+++ b/nx-X11/lib/X11/Xlibint.h
@@ -561,6 +561,14 @@ extern LockInfoPtr _Xglobal_lock;
dpy->request++
#endif
+/*
+ * MakeBigReq sets the CARD16 "req->length" to 0 and inserts a new CARD32
+ * length, after req->length, before the data in the request. The new length
+ * includes the "n" extra 32-bit words.
+ *
+ * Do not use MakeBigReq if there is no data already in the request.
+ * req->length must already be >= 2.
+ */
#ifdef WORD64
#define MakeBigReq(req,n) \
{ \
@@ -580,7 +588,7 @@ extern LockInfoPtr _Xglobal_lock;
CARD32 _BRlen = req->length - 1; \
req->length = 0; \
_BRdat = ((CARD32 *)req)[_BRlen]; \
- memmove(((char *)req) + 8, ((char *)req) + 4, _BRlen << 2); \
+ memmove(((char *)req) + 8, ((char *)req) + 4, (_BRlen - 1) << 2); \
((CARD32 *)req)[1] = _BRlen + n + 2; \
Data32(dpy, &_BRdat, 4); \
}
@@ -591,13 +599,20 @@ extern LockInfoPtr _Xglobal_lock;
CARD32 _BRlen = req->length - 1; \
req->length = 0; \
_BRdat = ((CARD32 *)req)[_BRlen]; \
- memmove(((char *)req) + 8, ((char *)req) + 4, _BRlen << 2); \
+ memmove(((char *)req) + 8, ((char *)req) + 4, (_BRlen - 1) << 2); \
((CARD32 *)req)[1] = _BRlen + n + 2; \
Data32(dpy, &_BRdat, 4); \
}
#endif
#endif
+/*
+ * SetReqLen increases the count of 32-bit words in the request by "n",
+ * or by "badlen" if "n" is too large.
+ *
+ * Do not use SetReqLen if "req" does not already have data after the
+ * xReq header. req->length must already be >= 2.
+ */
#define SetReqLen(req,n,badlen) \
if ((req->length + n) > (unsigned)65535) { \
if (dpy->bigreq_size) { \
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