Re: [PATCH] ALSA: Remove subsystem-specific malloc (1/8)

[Pekka Enberg <penberg@cs.helsinki.fi>]

On Wed, 2004-06-09 at 23:21, Arjan van de Ven wrote:
> how about making sure n*size doesn't overflow an int in this function?
> We had a few security holes due to that happening a while ago; might as
> well prevent it from happening entirely

Sure.

		Pekka

diff -urN linux-2.6.6/include/linux/slab.h kcalloc-2.6.6/include/linux/slab.h
--- linux-2.6.6/include/linux/slab.h	2004-06-09 22:56:11.874249056 +0300
+++ kcalloc-2.6.6/include/linux/slab.h	2004-06-09 23:03:10.597593432 +0300
@@ -95,6 +95,7 @@
 	return __kmalloc(size, flags);
 }
 
+extern void *kcalloc(size_t, size_t, int);
 extern void kfree(const void *);
 extern unsigned int ksize(const void *);
 
diff -urN linux-2.6.6/mm/slab.c kcalloc-2.6.6/mm/slab.c
--- linux-2.6.6/mm/slab.c	2004-06-09 22:59:13.081701336 +0300
+++ kcalloc-2.6.6/mm/slab.c	2004-06-09 23:50:06.592497136 +0300
@@ -2332,6 +2332,25 @@
 EXPORT_SYMBOL(kmem_cache_free);
 
 /**
+ * kcalloc - allocate memory for an array. The memory is set to zero.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate.
+ */
+void *kcalloc(size_t n, size_t size, int flags)
+{
+	if (n != 0 && size > INT_MAX / n)
+		return NULL;
+
+	void *ret = kmalloc(n * size, flags);
+	if (ret)
+		memset(ret, 0, n * size);
+	return ret;
+}
+
+EXPORT_SYMBOL(kcalloc);
+
+/**
  * kfree - free previously allocated memory
  * @objp: pointer returned by kmalloc.
  *