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MakeBigReq: don't move the last word, already handled by Data32

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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>.

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>
This commit is contained in:
Karl Tomlinson 2013-02-18 01:25:34 +00:00 • committed by Alan Coopersmith
parent 3cdb6c3a16
commit 39547d600a
1 changed files with 17 additions and 2 deletions
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19
include/X11/Xlibint.h
View file

@ -486,6 +486,14 @@ extern void *_XGetRequest(Display *dpy, CARD8 type, size_t len);
req = (xReq *) _XGetRequest(dpy, X_/**/name, SIZEOF(xReq))
#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 LONG64
#define MakeBigReq(req,n) \
{ \
@ -493,7 +501,7 @@ extern void *_XGetRequest(Display *dpy, CARD8 type, size_t len);
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); \
}
@ -504,12 +512,19 @@ extern void *_XGetRequest(Display *dpy, CARD8 type, size_t len);
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
/*
* 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.
*/
#ifndef __clang_analyzer__
#define SetReqLen(req,n,badlen) \
if ((req->length + n) > (unsigned)65535) { \