From: Karl Tomlinson <[email protected]> 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 <[email protected]>. https://bugzilla.mozilla.org/show_bug.cgi?id=803762 Reviewed-by: Jeff Muizelaar <[email protected]> Reviewed-by: Peter Hutterer <[email protected]> --- include/X11/Xlibint.h | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/include/X11/Xlibint.h b/include/X11/Xlibint.h index 80edeec..29c1598 100644 --- a/include/X11/Xlibint.h +++ b/include/X11/Xlibint.h @@ -502,6 +502,14 @@ 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 WORD64 #define MakeBigReq(req,n) \ { \ @@ -509,7 +517,7 @@ extern void *_XGetRequest(Display *dpy, CARD8 type, size_t len); unsigned long _BRlen = req->length - 1; \ req->length = 0; \ memcpy(_BRdat, ((char *)req) + (_BRlen << 2), 4); \ - memmove(((char *)req) + 8, ((char *)req) + 4, _BRlen << 2); \ + memmove(((char *)req) + 8, ((char *)req) + 4, (_BRlen - 1) << 2); \ memcpy(((char *)req) + 4, _BRdat, 4); \ Data32(dpy, (long *)&_BRdat, 4); \ } @@ -521,7 +529,7 @@ 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); \ } @@ -532,13 +540,20 @@ 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 #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) { \ -- 1.8.1.2 _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
