From: Kees Cook <keescook@chromium.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <mawilcox@microsoft.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Matthew Wilcox <willy@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v3 00/16] Provide saturating helpers for allocation
Date: Thu, 31 May 2018 21:18:10 -0700 [thread overview]
Message-ID: <CAGXu5jJeHD4Ouo9icjHk8oTCQLxjBvugVqQoZ7euDtLNtWCJ-A@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFzjt27tDoxU=iVo7N3cR_nVSRm5+nvTZg=+t2A4k_yNwA@mail.gmail.com>
On Thu, May 31, 2018 at 5:54 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Thu, May 31, 2018 at 7:43 PM Kees Cook <keescook@chromium.org> wrote:
>>
>> So, while nothing does:
>> kmalloc_array(a, b, ...) -> kmalloc(array_size(a, b), ...)
>> the treewide changes DO perform changes like this:
>> kmalloc(a * b, ...) -> kmalloc(array_size(a, b), ...)
>
> Ugh. I really really still absolutely despise this.
Heh. Yeah, I called this out specifically because I wasn't sure if
this was going to be okay. :P
> Why can't you just have a separate set of coccinelle scripts that do
> the simple and clean cases?
>
> So *before* doing any array_size() conversions, just do
>
> kzalloc(a*b, ...) -> kcalloc(a, b, ...)
> kmalloc(a*b,..) -> kmalloc_array(a,b, ...)
>
> and the obvious variations on that (devm_xyz() has all the same helpers).
Yup. I'll get started on it. I did have a version of a python script
that generated coccinelle scripts, but I started losing my mind. I'll
double-check if I can find a way to do some internal-to-Coccinelle
python to handle some of the variation directly, etc.
For those interested in the details: the complexity for me is in how
Coccinelle handles expressions (or my understanding of it's handling).
There's nothing in between "expression" and "identifier", so
"thing->field" is an expression not an identifier ("thing" is an
identifier), but "foo * bar" is _also_ an expression, so I have to
slowly peel away the "easy" stuff (sizeof, constants, etc) before
expressions to avoid collapsing factors into the wrong arguments (e.g.
kzalloc(a * b * c, ...) -> kcalloc(a * b, c, ...) is not desirable),
so there end up being a LOT of rules... I was able to compress
allocation families into a a regex, but without that, I'll end up with
the sizeof/const/etc rules times the family times the kalloc and
_array rules.
> Only after doing the ones that don't have the nice obvious helpers, do
> the remaining ones with array_size(), ie
>
> *alloc(a*b, ..) -> *alloc(array_size(a,b), ...)
>
> because that really makes for much less legible code.
>
> Hmm?
Sounds good. Thanks!
-Kees
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2018-06-01 4:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-01 0:42 [PATCH v3 00/16] Provide saturating helpers for allocation Kees Cook
2018-06-01 0:42 ` [PATCH v3 01/16] compiler.h: enable builtin overflow checkers and add fallback code Kees Cook
2018-06-01 0:42 ` [PATCH v3 02/16] lib: add runtime test of check_*_overflow functions Kees Cook
2018-06-01 0:42 ` [PATCH v3 03/16] lib: overflow: Report test failures Kees Cook
2018-06-01 0:42 ` [PATCH v3 04/16] overflow.h: Add allocation size calculation helpers Kees Cook
2018-06-01 0:42 ` [PATCH v3 05/16] lib: overflow: Add memory allocation overflow tests Kees Cook
2018-06-01 10:18 ` Andy Shevchenko
2018-06-01 0:42 ` [PATCH v3 06/16] mm: Use overflow helpers in kmalloc_array*() Kees Cook
2018-06-01 0:42 ` [PATCH v3 07/16] mm: Use overflow helpers in kvmalloc() Kees Cook
2018-06-01 0:42 ` [PATCH v3 08/16] device: Use overflow helpers for devm_kmalloc() Kees Cook
2018-06-01 0:42 ` [PATCH v3 09/16] treewide: Use struct_size() for kmalloc()-family Kees Cook
2018-06-01 0:42 ` [PATCH v3 10/16] treewide: Use struct_size() for vmalloc()-family Kees Cook
2018-06-01 0:42 ` [PATCH v3 11/16] treewide: Use struct_size() for devm_kmalloc() and friends Kees Cook
2018-06-01 0:42 ` [PATCH v3 12/16] treewide: Use array_size() for kmalloc()-family Kees Cook
2018-07-01 8:46 ` SF Markus Elfring
2018-07-01 8:46 ` SF Markus Elfring
2018-07-01 8:46 ` SF Markus Elfring
2018-07-01 9:03 ` Julia Lawall
2018-07-01 9:03 ` Julia Lawall
2018-07-01 9:03 ` Julia Lawall
2018-07-01 9:22 ` SF Markus Elfring
2018-07-01 9:22 ` SF Markus Elfring
2018-06-01 0:42 ` [PATCH v3 13/16] treewide: Use array_size() for kmalloc()-family, leftovers Kees Cook
2018-06-01 0:42 ` [PATCH v3 14/16] treewide: Use array_size() for vmalloc() Kees Cook
2018-06-01 0:42 ` [PATCH v3 15/16] treewide: Use array_size() for devm_*alloc()-like Kees Cook
2018-06-01 0:42 ` [PATCH v3 16/16] treewide: Use array_size() for devm_*alloc()-like, leftovers Kees Cook
2018-06-01 0:54 ` [PATCH v3 00/16] Provide saturating helpers for allocation Linus Torvalds
2018-06-01 4:18 ` Kees Cook [this message]
2018-06-01 13:50 Peter Rosin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAGXu5jJeHD4Ouo9icjHk8oTCQLxjBvugVqQoZ7euDtLNtWCJ-A@mail.gmail.com \
--to=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@rasmusvillemoes.dk \
--cc=mawilcox@microsoft.com \
--cc=torvalds@linux-foundation.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.