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Date: Thu, 15 Feb 2018 09:36:39 -0800
From: Matthew Wilcox <willy@...radead.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Joe Perches <joe@...ches.com>, Matthew Wilcox <mawilcox@...rosoft.com>,
linux-mm@...ck.org, Kees Cook <keescook@...omium.org>,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2 2/8] mm: Add kvmalloc_ab_c and kvzalloc_struct
On Wed, Feb 14, 2018 at 07:40:50PM -0800, Matthew Wilcox wrote:
> > a_foo = kvzalloc_struct_buf(struct foo, struct bar, nr_bars);
> >
> > or, of course.
> >
> > a_foo = kvzalloc_struct_buf(typeof(*a_foo), typeof(a_foo->bar[0]),
> > nr_bars);
> >
> > or whatever.
This version works, although it's more typing in the callers:
- attr_group = kvzalloc_struct(attr_group, attrs, i + 1,
+ attr_group = kvzalloc_struct(typeof(*attr_group), attrs, i + 1,
GFP_KERNEL);
...
- dev_dax = kvzalloc_struct(dev_dax, res, count, GFP_KERNEL);
+ dev_dax = kvzalloc_struct(struct dev_dax, res, count, GFP_KERNEL);
...
-#define kvzalloc_struct(p, member, n, gfp) \
- (typeof(p))kvzalloc_ab_c(n, \
- sizeof(*(p)->member) + __must_be_array((p)->member), \
- offsetof(typeof(*(p)), member), gfp)
+#define kvzalloc_struct(s, member, n, gfp) ({ \
+ s *__p; \
+ (s *)kvzalloc_ab_c(n, \
+ sizeof(*(__p)->member) + __must_be_array((__p)->member),\
+ offsetof(s, member), gfp); \
+})
Gives all the same checking as the current version, and doesn't involve
passing an uninitialised pointer to the macro.
It also looks pretty similar:
p = kvzalloc(sizeof(*p), GFP_KERNEL);
p = kvzalloc_struct(typeof(*p), array, count, GFP_KERNEL);
p = kvzalloc_array(sizeof(*p), count);
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