svn commit: r327796 - in head: share/man/man9 sys/kern sys/sys
Conrad Meyer
cem at FreeBSD.org
Wed Jan 10 21:49:47 UTC 2018
Author: cem
Date: Wed Jan 10 21:49:45 2018
New Revision: 327796
URL: https://svnweb.freebsd.org/changeset/base/327796
Log:
mallocarray(9): panic if the requested allocation would overflow
Additionally, move the overflow check logic out to WOULD_OVERFLOW() for
consumers to have a common means of testing for overflowing allocations.
WOULD_OVERFLOW() should be a secondary check -- on 64-bit platforms, just
because an allocation won't overflow size_t does not mean it is a sane size
to request. Callers should be imposing reasonable allocation limits far,
far, below overflow.
Discussed with: emaste, jhb, kp
Sponsored by: Dell EMC Isilon
Modified:
head/share/man/man9/malloc.9
head/sys/kern/kern_malloc.c
head/sys/sys/malloc.h
Modified: head/share/man/man9/malloc.9
==============================================================================
--- head/share/man/man9/malloc.9 Wed Jan 10 21:40:36 2018 (r327795)
+++ head/share/man/man9/malloc.9 Wed Jan 10 21:49:45 2018 (r327796)
@@ -29,7 +29,7 @@
.\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
.\" $FreeBSD$
.\"
-.Dd November 19, 2015
+.Dd January 10, 2018
.Dt MALLOC 9
.Os
.Sh NAME
@@ -154,6 +154,7 @@ If the request cannot be immediately fulfilled, the cu
to sleep to wait for resources to be released by other processes.
The
.Fn malloc ,
+.Fn mallocarray ,
.Fn realloc ,
and
.Fn reallocf
@@ -162,15 +163,13 @@ functions cannot return
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.
+would cause an integer overflow, the
+.Fn mallocarray
+function induces a panic.
.It Dv M_USE_RESERVE
Indicates that the system can use its reserve of memory to satisfy the
request.
Modified: head/sys/kern/kern_malloc.c
==============================================================================
--- head/sys/kern/kern_malloc.c Wed Jan 10 21:40:36 2018 (r327795)
+++ head/sys/kern/kern_malloc.c Wed Jan 10 21:49:45 2018 (r327796)
@@ -535,18 +535,12 @@ malloc(unsigned long size, struct malloc_type *mtp, in
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);
+ if (WOULD_OVERFLOW(nmemb, size))
+ panic("mallocarray: %zu * %zu overflowed", nmemb, size);
return (malloc(size * nmemb, type, flags));
}
Modified: head/sys/sys/malloc.h
==============================================================================
--- head/sys/sys/malloc.h Wed Jan 10 21:40:36 2018 (r327795)
+++ head/sys/sys/malloc.h Wed Jan 10 21:49:45 2018 (r327796)
@@ -41,6 +41,7 @@
#include <sys/queue.h>
#include <sys/_lock.h>
#include <sys/_mutex.h>
+#include <machine/_limits.h>
#define MINALLOCSIZE UMA_SMALLEST_UNIT
@@ -192,6 +193,20 @@ void *reallocf(void *addr, unsigned long size, struct
int flags) __result_use_check __alloc_size(2);
struct malloc_type *malloc_desc2type(const char *desc);
+
+/*
+ * 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))
+static inline bool
+WOULD_OVERFLOW(size_t nmemb, size_t size)
+{
+
+ return ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+ nmemb > 0 && __SIZE_T_MAX / nmemb < size);
+}
+#undef MUL_NO_OVERFLOW
#endif /* _KERNEL */
#endif /* !_SYS_MALLOC_H_ */
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