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Index: head/share/man/man9/malloc.9
===================================================================
--- head/share/man/man9/malloc.9
+++ head/share/man/man9/malloc.9
@@ -45,6 +45,8 @@
.In sys/malloc.h
.Ft void *
.Fn malloc "unsigned long size" "struct malloc_type *type" "int flags"
+.Ft void *
+.Fn mallocarray "size_t nmemb" "size_t size" "struct malloc_type *type" "int flags"
.Ft void
.Fn free "void *addr" "struct malloc_type *type"
.Ft void *
@@ -64,6 +66,14 @@
.Fa size .
.Pp
The
+.Fn mallocarray
+function allocates uninitialized memory in kernel address space for an
+array of
+.Fa nmemb
+entries whose size is specified by
+.Fa size .
+.Pp
+The
.Fn free
function releases memory at address
.Fa addr
@@ -152,6 +162,15 @@
if
.Dv M_WAITOK
is specified.
+The
+.Fn mallocarray
+function can return
+.Dv NULL
+if the multiplication of
+.Fa nmemb
+and
+.Fa size
+would cause an integer overflow.
.It Dv M_USE_RESERVE
Indicates that the system can use its reserve of memory to satisfy the
request.
Index: head/sys/kern/kern_malloc.c
===================================================================
--- head/sys/kern/kern_malloc.c
+++ head/sys/kern/kern_malloc.c
@@ -4,6 +4,7 @@
* Copyright (c) 1987, 1991, 1993
* The Regents of the University of California.
* Copyright (c) 2005-2009 Robert N. M. Watson
+ * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net> (mallocarray)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -532,6 +533,22 @@
va = redzone_setup(va, osize);
#endif
return ((void *) va);
+}
+
+/*
+ * 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) * 8 / 2))
+void *
+mallocarray(size_t nmemb, size_t size, struct malloc_type *type, int flags)
+{
+
+ if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+ nmemb > 0 && SIZE_MAX / nmemb < size)
+ return (NULL);
+
+ return (malloc(size * nmemb, type, flags));
}
/*
Index: head/sys/sys/malloc.h
===================================================================
--- head/sys/sys/malloc.h
+++ head/sys/sys/malloc.h
@@ -177,6 +177,9 @@
void free(void *addr, struct malloc_type *type);
void *malloc(unsigned long size, struct malloc_type *type, int flags)
__malloc_like __result_use_check __alloc_size(1);
+void *mallocarray(size_t nmemb, size_t size, struct malloc_type *type,
+ int flags) __malloc_like __result_use_check
+ __alloc_size(1) __alloc_size(2);
void malloc_init(void *);
int malloc_last_fail(void);
void malloc_type_allocated(struct malloc_type *type, unsigned long size);

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