Implement reallocarray()

Stateless and I stumbled upon this issue while discussing the
semantics of read, accepting a size_t but only being able to return
ssize_t, effectively lacking the ability to report successful
reads > SSIZE_MAX.
The discussion went along and we came to the topic of input-based
memory allocations. Basically, it was possible for the argument
to a memory-allocation-function to overflow, leading to a segfault
later.
The OpenBSD-guys came up with the ingenious reallocarray-function,
and I implemented it as ereallocarray, which automatically returns
on error.
Read more about it here[0].

A simple testcase is this (courtesy to stateless):
$ sbase-strings -n (2^(32|64) / 4)

This will segfault before this patch and properly return an OOM-
situation afterwards (thanks to the overflow-check in reallocarray).

[0]: http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/calloc.3

Makefile

@@ -57,6 +57,7 @@ LIBUTILSRC =\
 	libutil/md5.c\
 	libutil/mode.c\
 	libutil/putword.c\
+	libutil/reallocarray.c\
 	libutil/recurse.c\
 	libutil/rm.c\
 	libutil/sha1.c\

col.c

@@ -177,7 +177,7 @@ allocbuf(void)
 {
 	char **bp;
 
-	buff = emalloc(sizeof(*buff) * pagsize);
+	buff = ereallocarray(buff, pagsize, sizeof(*buff));
 	for (bp = buff; bp < &buff[pagsize]; ++bp)
 		*bp = emalloc(NCOLS);
 }

cut.c

@@ -56,7 +56,7 @@ parselist(char *str)
 		if (*s == ',')
 			n++;
 	}
-	r = emalloc(n * sizeof(Range));
+	r = ereallocarray(r, n, sizeof(*r));
 	for (s = str; n; n--, s++) {
 		r->min = (*s == '-') ? 1 : strtoul(s, &s, 10);
 		r->max = (*s == '-') ? strtoul(s + 1, &s, 10) : r->min;

expand.c

@@ -19,12 +19,12 @@ parselist(const char *s)
 	for (i = 0; (p = strsep(&tmp, " ,")); i++) {
 		if (*p == '\0')
 			eprintf("empty field in tablist\n");
-		tablist = erealloc(tablist, (i + 1) * sizeof(*tablist));
+		tablist = ereallocarray(tablist, i + 1, sizeof(*tablist));
 		tablist[i] = estrtonum(p, 1, MIN(LLONG_MAX, SIZE_MAX));
 		if (i > 0 && tablist[i - 1] >= tablist[i])
 			eprintf("tablist must be ascending\n");
 	}
-	tablist = erealloc(tablist, (i + 1) * sizeof(*tablist));
+	tablist = ereallocarray(tablist, i + 1, sizeof(*tablist));
 	/* tab length = 1 for the overflowing case later in the matcher */
 	tablist[i] = 1;
 	return i;

find.c

@@ -380,7 +380,7 @@ pri_exec(Arg *arg)
 
 		/* if we have too many files, realloc (with space for NULL termination) */
 		if (e->u.p.next + 1 == e->u.p.cap)
-			e->argv = erealloc(e->argv, (e->u.p.cap *= 2) * sizeof(*e->argv));
+			e->argv = ereallocarray(e->argv, e->u.p.cap *= 2, sizeof(*e->argv));
 
 		e->argv[e->u.p.next++] = estrdup(arg->path);
 		e->u.p.filelen += len + sizeof(arg->path);
@@ -595,7 +595,7 @@ get_exec_arg(char *argv[], Extra *extra)
 		e->u.p.arglen = e->u.p.filelen = 0;
 		e->u.p.first = e->u.p.next = arg - argv - 1;
 		e->u.p.cap = (arg - argv) * 2;
-		e->argv = emalloc(e->u.p.cap * sizeof(*e->argv));
+		e->argv = ereallocarray(e->argv, e->u.p.cap, sizeof(*e->argv));
 
 		for (arg = argv, new = e->argv; *arg; arg++, new++) {
 			*new = *arg;
@@ -604,7 +604,7 @@ get_exec_arg(char *argv[], Extra *extra)
 		arg++; /* due to our extra NULL */
 	} else {
 		e->argv = argv;
-		e->u.s.braces = emalloc(++nbraces * sizeof(*e->u.s.braces)); /* ++ for NULL */
+		e->u.s.braces = ereallocarray(e->u.s.braces, ++nbraces, sizeof(*e->u.s.braces)); /* ++ for NULL */
 
 		for (arg = argv, braces = e->u.s.braces; *arg; arg++)
 			if (!strcmp(*arg, "{}"))
@@ -632,7 +632,7 @@ get_ok_arg(char *argv[], Extra *extra)
 	*arg = NULL;
 
 	o->argv = argv;
-	o->braces = emalloc(++nbraces * sizeof(*o->braces));
+	o->braces = ereallocarray(o->braces, ++nbraces, sizeof(*o->braces));
 
 	for (arg = argv, braces = o->braces; *arg; arg++)
 		if (!strcmp(*arg, "{}"))
@@ -824,7 +824,7 @@ parse(int argc, char **argv)
 	 * https://en.wikipedia.org/wiki/Shunting-yard_algorithm
 	 * read from infix, resulting rpn ends up in rpn, next position in rpn is out
 	 * push operators onto stack, next position in stack is top */
-	rpn = emalloc((ntok + gflags.print) * sizeof(*rpn));
+	rpn = ereallocarray(rpn, ntok + gflags.print, sizeof(*rpn));
 	for (tok = infix, out = rpn, top = stack; tok->type != END; tok++) {
 		switch (tok->type) {
 		case PRIM: *out++ = *tok; break;

libutil/reallocarray.c

@@ -0,0 +1,51 @@
+/*	$OpenBSD: reallocarray.c,v 1.1 2014/05/08 21:43:49 deraadt Exp $	*/
+/*
+ * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "../util.h"
+
+/*
+ * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
+ * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
+ */
+#define MUL_NO_OVERFLOW	(1UL << (sizeof(size_t) * 4))
+
+void *
+reallocarray(void *optr, size_t nmemb, size_t size)
+{
+	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	return realloc(optr, size * nmemb);
+}
+
+void *
+ereallocarray(void *optr, size_t nmemb, size_t size)
+{
+	void *p;
+
+	if (!(p = reallocarray(optr, nmemb, size)))
+		eprintf("reallocarray: out of memory\n");
+
+	return p;
+}

ls.c

@@ -217,7 +217,7 @@ lsdir(const char *path)
 			mkent(&ent, d->d_name, Fflag || lflag || pflag || iflag || Rflag, Lflag);
 			ls(&ent, Rflag);
 		} else {
-			ents = erealloc(ents, ++n * sizeof(*ents));
+			ents = ereallocarray(ents, ++n, sizeof(*ents));
 			name = p = estrdup(d->d_name);
 			if (qflag) {
 				q = d->d_name;
@@ -269,7 +269,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	struct entry *ents;
+	struct entry *ents = NULL;
 	size_t i;
 
 	ARGBEGIN {
@@ -341,7 +341,7 @@ main(int argc, char *argv[])
 	if (argc == 0)
 		*--argv = ".", argc++;
 
-	ents = emalloc(argc * sizeof(*ents));
+	ents = ereallocarray(ents, argc, sizeof(*ents));
 
 	for (i = 0; i < argc; i++)
 		mkent(&ents[i], argv[i], 1, Hflag || Lflag);

paste.c

@@ -85,8 +85,8 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	struct fdescr *dsc;
+	struct fdescr *dsc = NULL;
-	Rune  *delim;
+	Rune  *delim = NULL;
 	size_t i, len;
 	int    seq = 0;
 	char  *adelim = "\t";
@@ -107,11 +107,11 @@ main(int argc, char *argv[])
 
 	/* populate delimiters */
 	unescape(adelim);
-	delim = emalloc((utflen(adelim) + 1) * sizeof(*delim));
+	delim = ereallocarray(delim, utflen(adelim) + 1, sizeof(*delim));
 	len = utftorunestr(adelim, delim);
 
 	/* populate file list */
-	dsc = emalloc(argc * sizeof(*dsc));
+	dsc = ereallocarray(dsc, argc, sizeof(*dsc));
 
 	for (i = 0; i < argc; i++) {
 		if (strcmp(argv[i], "-") == 0)

printf.c

@@ -111,7 +111,7 @@ main(int argc, char *argv[])
 			break;
 		case 'c':
 			unescape(arg);
-			rarg = emalloc((utflen(arg) + 1) * sizeof(*rarg));
+			rarg = ereallocarray(rarg, utflen(arg) + 1, sizeof(*rarg));
 			utftorunestr(arg, rarg);
 			efputrune(rarg, stdout, "<stdout>");
 			free(rarg);
@@ -125,7 +125,7 @@ main(int argc, char *argv[])
 			if (arg[j] == '\'' || arg[j] == '\"') {
 				arg += j + 1;
 				unescape(arg);
-				rarg = emalloc((utflen(arg) + 1) * sizeof(*rarg));
+				rarg = ereallocarray(rarg, utflen(arg) + 1, sizeof(*rarg));
 				utftorunestr(arg, rarg);
 				num = rarg[0];
 			} else

sed.c

@@ -275,7 +275,7 @@ resize(void **ptr, size_t *nmemb, size_t size, size_t new_nmemb, void **next)
 	void *n, *tmp;
 
 	if (new_nmemb) {
-		tmp = erealloc(*ptr, new_nmemb * size);
+		tmp = ereallocarray(*ptr, new_nmemb, size);
 	} else { /* turns out realloc(*ptr, 0) != free(*ptr) */
 		free(*ptr);
 		tmp = NULL;
@@ -596,7 +596,10 @@ chompr(char *s, Rune rune)
 Rune *
 strtorunes(char *s, size_t nrunes)
 {
-	Rune *rs = emalloc(sizeof(*rs) * nrunes + 1), *rp = rs;
+	Rune *rs = NULL, *rp;
+
+	rs = ereallocarray(rs, nrunes + 1, sizeof(*rs));
+	rp = rs;
 
 	while (nrunes--)
 		s += chartorune(rp++, s);

strings.c

@@ -11,11 +11,11 @@ static char *format = "";
 static void
 strings(FILE *fp, const char *fname, size_t len)
 {
-	Rune r, *rbuf;
+	Rune r, *rbuf = NULL;
 	size_t i, bread;
 	off_t off;
 
-	rbuf = emalloc(len * sizeof(*rbuf));
+	rbuf = ereallocarray(rbuf, len, sizeof(*rbuf));
 
 	for (off = 0, i = 0; (bread = efgetrune(&r, fp, fname)); ) {
 		off += bread;

tr.c

@@ -71,16 +71,16 @@ rstrmatch(Rune *r, char *s, size_t n)
 static size_t
 makeset(char *str, struct range **set, int (**check)(Rune))
 {
-	Rune  *rstr;
+	Rune  *rstr = NULL;
 	size_t len, i, j, m, n;
 	size_t q, setranges = 0;
 	int    factor, base;
 
 	/* rstr defines at most len ranges */
 	unescape(str);
-	rstr = emalloc((utflen(str) + 1) * sizeof(*rstr));
+	rstr = ereallocarray(rstr, utflen(str) + 1, sizeof(*rstr));
 	len = utftorunestr(str, rstr);
-	*set = emalloc(len * sizeof(**set));
+	*set = ereallocarray(*set, len, sizeof(**set));
 
 	for (i = 0; i < len; i++) {
 		if (rstr[i] == '[') {

unexpand.c

@@ -19,12 +19,12 @@ parselist(const char *s)
 	for (i = 0; (p = strsep(&tmp, " ,")); i++) {
 		if (*p == '\0')
 			eprintf("empty field in tablist\n");
-		tablist = erealloc(tablist, (i + 1) * sizeof(*tablist));
+		tablist = ereallocarray(tablist, i + 1, sizeof(*tablist));
 		tablist[i] = estrtonum(p, 1, MIN(LLONG_MAX, SIZE_MAX));
 		if (i > 0 && tablist[i - 1] >= tablist[i])
 			eprintf("tablist must be ascending\n");
 	}
-	tablist = erealloc(tablist, (i + 1) * sizeof(*tablist));
+	tablist = ereallocarray(tablist, i + 1, sizeof(*tablist));
 	return i;
 }
 

util.h

@@ -26,6 +26,8 @@ void apathmax(char **, size_t *);
 void *ecalloc(size_t, size_t);
 void *emalloc(size_t);
 void *erealloc(void *, size_t);
+void *reallocarray(void *, size_t, size_t);
+void *ereallocarray(void *, size_t, size_t);
 char *estrdup(const char *);
 char *estrndup(const char *, size_t);
 void *encalloc(int, size_t, size_t);