Add reallocarray function

The reallocarray function is an extension from OpenBSD.  It is an
integer-overflow-safe replacement for realloc(p, X*Y) and
malloc(X*Y) (realloc(NULL, X*Y)).  It can therefore help in preventing
certain security issues in code.

This is an updated version of a patch originally submitted by Rüdiger
Sonderfeld in May 2014 [1].

Checked on i686-linux-gnu and x86_64-linux-gnu.

[1] <https://sourceware.org/ml/libc-alpha/2014-05/msg00481.html>.

2017-05-30  Dennis Wölfing  <denniswoelfing@gmx.de>
            Rüdiger Sonderfeld  <ruediger@c-plusplus.de>

	* include/stdlib.h (__libc_reallocarray): New declaration.
	* malloc/Makefile (routines): Add reallocarray.
	(tests): Add tst-reallocarray.c.
	* malloc/Versions: Add reallocarray and __libc_reallocarray.
	* malloc/malloc-internal.h (check_mul_overflow_size_t): New inline
	function.
	* malloc/malloc.h (reallocarray): New declaration.
	* stdlib/stdlib.h (reallocarray): Likewise.
	* malloc/reallocarray.c: New file.
	* malloc/tst-reallocarray.c: New test file.
	* manual/memory.texi: Document reallocarray.
	* sysdeps/unix/sysv/linux/aarch64/libc.abilist: Add reallocarray.
	* sysdeps/unix/sysv/linux/alpha/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/arm/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/hppa/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/i386/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/ia64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/nios2/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist:
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sh/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx32/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tile/tilegx/tilegx64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/tilepro/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: Likewise.

1 files changed, 37 insertions, 0 deletions

diff --git a/malloc/reallocarray.c b/malloc/reallocarray.c
new file mode 100644
index 0000000000..07562c30c9
--- /dev/null
+++ b/malloc/reallocarray.c
@@ -0,0 +1,37 @@
+/* Change the size of an allocated block.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <malloc.h>
+#include <malloc/malloc-internal.h>
+
+void *
+__libc_reallocarray (void *optr, size_t nmemb, size_t elem_size)
+{
+  size_t bytes;
+  if (check_mul_overflow_size_t (nmemb, elem_size, &bytes))
+    {
+      __set_errno (ENOMEM);
+      return 0;
+    }
+  else
+    return realloc (optr, bytes);
+}
+libc_hidden_def (__libc_reallocarray)
+
+weak_alias (__libc_reallocarray, reallocarray)