libpanel: fix memory corruption bug in plinitentry(), add pl_erealloc()

sys/src/cmd/mothra/libpanel/entry.c

@@ -34,8 +34,7 @@ void pl_pasteentry(Panel *p, char *s){
 	ep=p->data;
 	n=ep->entp-ep->entry;
 	m=strlen(s);
-	if((e=realloc(ep->entry,n+m+SLACK))==0)
-		return;
+	e=pl_erealloc(ep->entry,n+m+SLACK);
 	ep->entry=e;
 	e+=n;
 	strncpy(e, s, m);
@@ -131,11 +130,7 @@ void pl_typeentry(Panel *p, Rune c){
 		ep->entp+=runetochar(ep->entp, &c);
 		if(ep->entp>ep->eent){
 			n=ep->entp-ep->entry;
-			ep->entry=realloc(ep->entry, n+100+SLACK);
-			if(ep->entry==0){
-				fprint(2, "can't realloc in pl_typeentry\n");
-				exits("no mem");
-			}
+			ep->entry=pl_erealloc(ep->entry, n+100+SLACK);
 			ep->entp=ep->entry+n;
 			ep->eent=ep->entp+100;
 		}
@@ -155,7 +150,7 @@ void pl_freeentry(Panel *p){
 	Entry *ep;
 	ep = p->data;
 	free(ep->entry);
-	ep->entry = ep->eent = 0;
+	ep->entry = ep->eent = ep->entp = 0;
 }
 void plinitentry(Panel *v, int flags, int wid, char *str, void (*hit)(Panel *, char *)){
 	int elen;
@@ -174,8 +169,7 @@ void plinitentry(Panel *v, int flags, int wid, char *str, void (*hit)(Panel *, c
 	v->paste=pl_pasteentry;
 	elen=100;
 	if(str) elen+=strlen(str);
-	if(ep->entry==nil)
-		ep->entry=pl_emalloc(elen+SLACK);
+	ep->entry=pl_erealloc(ep->entry, elen+SLACK);
 	ep->eent=ep->entry+elen;
 	strecpy(ep->entry, ep->eent, str ? str : "");
 	ep->entp=ep->entry+strlen(ep->entry);

sys/src/cmd/mothra/libpanel/mem.c

@@ -14,6 +14,16 @@ void *pl_emalloc(int n){
 	setmalloctag(v, getcallerpc(&n));
 	return v;
 }
+void *pl_erealloc(void *v, int n)
+{
+	v=realloc(v, n);
+	if(v==0){
+		fprint(2, "Can't realloc!\n");
+		exits("no mem");
+	}
+	setrealloctag(v, getcallerpc(&v));
+	return v;
+}
 void pl_unexpected(Panel *g, char *rou){
 	fprint(2, "%s called unexpectedly (%s %lux)\n", rou, g->kind, (ulong)g);
 	abort();

sys/src/cmd/mothra/libpanel/pldefs.h

@@ -45,6 +45,7 @@ enum{
 };
 Panel *pl_newpanel(Panel *, int);	/* make a new Panel, given parent & data size */
 void *pl_emalloc(int);			/* allocate some space, exit on error */
+void *pl_erealloc(void*,int);		/* reallocate some space, exit on error */
 void pl_print(Panel *);			/* print a Panel tree */
 Panel *pl_ptinpanel(Point, Panel *);	/* highest-priority subpanel containing point */
 /*

sys/src/cmd/mothra/libpanel/rtext.c

@@ -302,8 +302,7 @@ char *plrtsnarftext(Rtext *w){
 		n = strlen(w->text)+64;
 		if(p+n >= e){
 			n = (p+n+64)-b;
-			if((t = realloc(b, n))==0)
-				break;
+			t = pl_erealloc(b, n);
 			p = t+(p-b);
 			e = t+n;
 			b = t;

sys/src/cmd/mothra/libpanel/snarf.c

@@ -17,16 +17,14 @@ void plputsnarf(char *s){
 }
 char *plgetsnarf(void){
 	int fd, n, r;
-	char *s, *x;
+	char *s;
 
 	if((fd=open("/dev/snarf", OREAD))<0)
 		return nil;
 	n=0;
 	s=nil;
 	for(;;){
-		if((x=realloc(s, n+1024))==0)
-			break;
-		s=x;
+		s=pl_erealloc(s, n+1024);
 		if((r = read(fd, s+n, 1024)) <= 0)
 			break;
 		n += r;

sys/src/cmd/mothra/libpanel/textwin.c

@@ -66,11 +66,7 @@ void tw_storeloc(Textwin *t, int l, Point p){
 	int nloc;
 	if(l>=t->eloc-t->loc){
 		nloc=l+SLACK;
-		t->loc=realloc(t->loc, nloc*sizeof(Point));
-		if(t->loc==0){
-			fprint(2, "No mem in tw_storeloc\n");
-			exits("no mem");
-		}
+		t->loc=pl_erealloc(t->loc, nloc*sizeof(Point));
 		t->eloc=t->loc+nloc;
 	}
 	t->loc[l]=p;
@@ -390,16 +386,13 @@ void tw_relocate(Textwin *t, int first, int last, Point dst){
  */
 void twreplace(Textwin *t, int r0, int r1, Rune *ins, int nins){
 	int olen, nlen, tlen, dtop;
-	Rune *ntext;
 	olen=t->etext-t->text;
 	nlen=olen+nins-(r1-r0);
 	tlen=t->eslack-t->text;
 	if(nlen>tlen){
 		tlen=nlen+SLACK;
-		if((ntext=realloc(t->text, tlen*sizeof(Rune)))==0)
-			return;
-		t->text=ntext;
-		t->eslack=ntext+tlen;
+		t->text=pl_erealloc(t->text, tlen*sizeof(Rune));
+		t->eslack=t->text+tlen;
 	}
 	if(olen!=nlen)
 		memmove(t->text+r0+nins, t->text+r1, (olen-r1)*sizeof(Rune));