From 1bb7064e52f2efe021728e66eb627bae7c9fae71 Mon Sep 17 00:00:00 2001
From: otto <>
Date: Wed, 21 Nov 2018 06:57:04 +0000
Subject: [PATCH] Introducing malloc_usable_size() was a mistake. While some
 other libs have it, it is a function that is considered harmful, so:

Delete malloc_usable_size(). It is a function that blurs the line
between malloc managed memory and application managed memory and
exposes some of the internal workings of malloc.  If an application
relies on that, it is likely to break using another implementation
of malloc.  If you want usable size x, just allocate x bytes. ok
deraadt@ and other devs
---
 src/include/stdlib.h         |  3 +-
 src/lib/libc/stdlib/malloc.3 | 31 ++------------
 src/lib/libc/stdlib/malloc.c | 79 +-----------------------------------
 3 files changed, 6 insertions(+), 107 deletions(-)

diff --git a/src/include/stdlib.h b/src/include/stdlib.h
index b0f3dd14..7a26ed90 100644
--- a/src/include/stdlib.h
+++ b/src/include/stdlib.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: stdlib.h,v 1.74 2018/11/18 16:15:18 otto Exp $	*/
+/*	$OpenBSD: stdlib.h,v 1.75 2018/11/21 06:57:04 otto Exp $	*/
 /*	$NetBSD: stdlib.h,v 1.25 1995/12/27 21:19:08 jtc Exp $	*/
 
 /*-
@@ -112,7 +112,6 @@ long	 labs(long);
 ldiv_t	 ldiv(long, long);
 void	*malloc(size_t);
 #if __BSD_VISIBLE
-size_t	 malloc_usable_size(void *);
 void	freezero(void *, size_t)
 		 __attribute__ ((__bounded__(__buffer__,1,2)));
 void	*reallocarray(void *, size_t, size_t);
diff --git a/src/lib/libc/stdlib/malloc.3 b/src/lib/libc/stdlib/malloc.3
index c1776f61..c0472ee2 100644
--- a/src/lib/libc/stdlib/malloc.3
+++ b/src/lib/libc/stdlib/malloc.3
@@ -30,9 +30,9 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: malloc.3,v 1.119 2018/11/18 16:15:18 otto Exp $
+.\"	$OpenBSD: malloc.3,v 1.120 2018/11/21 06:57:04 otto Exp $
 .\"
-.Dd $Mdocdate: November 18 2018 $
+.Dd $Mdocdate: November 21 2018 $
 .Dt MALLOC 3
 .Os
 .Sh NAME
@@ -43,8 +43,7 @@
 .Nm reallocarray ,
 .Nm recallocarray ,
 .Nm freezero ,
-.Nm aligned_alloc ,
-.Nm malloc_usable_size
+.Nm aligned_alloc
 .Nd memory allocation and deallocation
 .Sh SYNOPSIS
 .In stdlib.h
@@ -65,7 +64,6 @@
 .Ft void *
 .Fn aligned_alloc "size_t alignment" "size_t size"
 .Ft size_t
-.Fn malloc_usable_size "void *ptr"
 .Vt char *malloc_options ;
 .Sh DESCRIPTION
 The standard functions
@@ -236,25 +234,6 @@ If
 is not a multiple of
 .Fa alignment ,
 behavior is undefined.
-.Pp
-The
-.Fn malloc_usable_size
-function returns the actual size of the allocated memory pointed to by
-.Va ptr .
-If
-.Va ptr
-is
-.Dv NULL ,
-it returns 0.
-If
-.Va ptr
-was never returned by an allocation function or freed before,
-the behavior is undefined.
-This function should not be relied upon since it exposes some of the internal
-workings of the
-.Fn malloc
-family of functions.
-Writing beyond the requested size introduces undefined behavior.
 .Sh RETURN VALUES
 Upon successful completion, the allocation functions
 return a pointer to the allocated space; otherwise,
@@ -640,9 +619,7 @@ function appeared in
 .Ox 6.2 .
 The
 .Fn aligned_alloc
-and
-.Fn malloc_usable_size
-functions appeared in
+function appeared in
 .Ox 6.5 .
 .Sh CAVEATS
 When using
diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index 513defcc..0912b904 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.253 2018/11/19 22:50:24 guenther Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.254 2018/11/21 06:57:04 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -1466,83 +1466,6 @@ freezero(void *ptr, size_t sz)
 }
 DEF_WEAK(freezero);
 
-static size_t
-osize(struct dir_info *argpool, void *p)
-{
-	struct dir_info *pool;
-	struct region_info *r;
-	char *saved_function;
-	size_t sz;
-	int i;
-
-	pool = argpool;
-	r = find(pool, p);
-	if (r == NULL) {
-		if (mopts.malloc_mt)  {
-			for (i = 0; i < _MALLOC_MUTEXES; i++) {
-				if (i == argpool->mutex)
-					continue;
-				pool->active--;
-				_MALLOC_UNLOCK(pool->mutex);
-				pool = mopts.malloc_pool[i];
-				_MALLOC_LOCK(pool->mutex);
-				pool->active++;
-				r = find(pool, p);
-				if (r != NULL) {
-					saved_function = pool->func;
-					pool->func = argpool->func;
-					break;
-				}
-			}
-		}
-		if (r == NULL)
-			wrterror(argpool, "bogus pointer (double free?) %p", p);
-	}
-
-	REALSIZE(sz, r);
-	if (sz > MALLOC_MAXCHUNK) {
-		if (MALLOC_MOVE_COND(sz))
-			sz = MALLOC_PAGESIZE - ((char *)p - (char *)r->p);
-		else
-			sz = PAGEROUND(sz);
-	}
-	if (argpool != pool) {
-		pool->active--;
-		pool->func = saved_function;
-		_MALLOC_UNLOCK(pool->mutex);
-		_MALLOC_LOCK(argpool->mutex);
-		argpool->active++;
-	}
-	return sz;
-}
-
-size_t
-malloc_usable_size(void *ptr)
-{
-	struct dir_info *d;
-	int saved_errno = errno;
-	size_t sz;
-
-	/* This is legal. */
-	if (ptr == NULL)
-		return 0;
-
-	d = getpool();
-	if (d == NULL)
-		wrterror(d, "malloc_usable_size() called before allocation");
-	_MALLOC_LOCK(d->mutex);
-	d->func = "malloc_usable_size";
-	if (d->active++) {
-		malloc_recurse(d);
-		return 0;
-	}
-	sz = osize(d, ptr);
-	d->active--;
-	_MALLOC_UNLOCK(d->mutex);
-	errno = saved_errno;
-	return sz;
-}
-
 static void *
 orealloc(struct dir_info *argpool, void *p, size_t newsz, void *f)
 {