Bug #6428, #16458, #21464: Fix crash due to uninitialized VModMap fields.

In ProcXkbGetKbdByName, mrep.firstVModMapKey, .nVModMapKeys and
.totalVModMapKeys were not initialized, contained random values and caused
accesses to unallocated and later modified memory, causing
XkbSizeVirtualModMap and XkbWriteVirtualModMap to see different number of
nonzero values, resulting in writes past the end of an array in XkbSendMap.

This patch initializes those values sensibly and reverts commits 5c0a2088 and
6dd4fc46, which have been plain non-sense.

Signed-off-by: Tomas Janousek <tomi@nomi.cz>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/xkb/xkb.c b/xkb/xkb.c
index e7c9a312d..3688bfcc0 100644
--- a/xkb/xkb.c
+++ b/xkb/xkb.c
@@ -1308,7 +1308,7 @@ XkbSizeVirtualModMap(XkbDescPtr xkb,xkbGetMapReply *rep)
 	rep->totalVModMapKeys= 0;
 	return 0;
     }
-    for (nRtrn=i=0;i<rep->nVModMapKeys-1;i++) {
+    for (nRtrn=i=0;i<rep->nVModMapKeys;i++) {
 	if (xkb->server->vmodmap[i+rep->firstVModMapKey]!=0)
 	    nRtrn++;
     }
@@ -1327,7 +1327,7 @@ unsigned short *	pMap;
 
     wire= (xkbVModMapWireDesc *)buf;
     pMap= &xkb->server->vmodmap[rep->firstVModMapKey];
-    for (i=0;i<rep->nVModMapKeys-1;i++,pMap++) {
+    for (i=0;i<rep->nVModMapKeys;i++,pMap++) {
 	if (*pMap!=0) {
 	    wire->key= i+rep->firstVModMapKey;
 	    wire->vmods= *pMap;
@@ -5668,7 +5668,7 @@ ProcXkbGetKbdByName(ClientPtr client)
 	    mrep.present = 0;
 	    mrep.totalSyms = mrep.totalActs =
 		mrep.totalKeyBehaviors= mrep.totalKeyExplicit= 
-		mrep.totalModMapKeys= 0;
+		mrep.totalModMapKeys= mrep.totalVModMapKeys= 0;
 	    if (rep.reported&(XkbGBN_TypesMask|XkbGBN_ClientSymbolsMask)) {
 		mrep.present|= XkbKeyTypesMask;
 		mrep.firstType = 0;
@@ -5694,6 +5694,8 @@ ProcXkbGetKbdByName(ClientPtr client)
 			mrep.firstKeyExplicit = new->min_key_code;
 		mrep.nKeyActs = mrep.nKeyBehaviors = 
 			mrep.nKeyExplicit = XkbNumKeys(new);
+		mrep.firstVModMapKey= new->min_key_code;
+		mrep.nVModMapKeys= XkbNumKeys(new);
 	    }
 	    else {
 		mrep.virtualMods= 0;