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From: Nick Desaulniers <ndesaulniers@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
	Josef Bacik <josef@toxicpanda.com>,  Jens Axboe <axboe@kernel.dk>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sasha Levin <sashal@kernel.org>,
	llvm@lists.linux.dev,  stable <stable@vger.kernel.org>,
	Arnd Bergmann <arnd@kernel.org>,
	 Naresh Kamboju <naresh.kamboju@linaro.org>,
	Nathan Chancellor <nathan@kernel.org>,
	 Stephen Rothwell <sfr@canb.auug.org.au>,
	Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH 5.10] overflow.h: use new generic division helpers to avoid / operator
Date: Tue, 14 Sep 2021 12:50:44 -0700	[thread overview]
Message-ID: <CAKwvOdk9yqEMLTAxgZNmHgRSww0AnJ-x9qd7HK3v2Vepi1BdLw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wjf6ABFwPdsbk2674DwSLQCH0jr7w-BYvG-f2nvRQDqtQ@mail.gmail.com>

On Tue, Sep 14, 2021 at 12:46 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Tue, Sep 14, 2021 at 12:10 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > Isn't the parameter `blksize` of `nbd_set_size` declared as `loff_t`?
>
> So?
>
> I'm not seeing your point.
>
> We've checked the range of it - in loff_t.
>
> So the *value* is already checked, and most definitely fits in 'unsigned long'.
>
> So __ffs() is perfectly fine. It will truncate that loff_t to a sane type.
>
> What is the problem you're trying to solve?

Just making sure __ffs() works as expected should blksize > LONG_MAX
on 32b targets.  I don't see the range check you're referring to.
loff_t is a long long, yeah?
-- 
Thanks,
~Nick Desaulniers

  reply	other threads:[~2021-09-14 19:50 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-13 20:32 [PATCH 5.10] overflow.h: use new generic division helpers to avoid / operator Nick Desaulniers
2021-09-13 20:32 ` Nick Desaulniers
2021-09-13 21:05 ` Rasmus Villemoes
2021-09-14  0:23   ` [PATCH v2] " Nick Desaulniers
2021-09-14  0:23     ` Nick Desaulniers
2021-09-14 17:22     ` Greg Kroah-Hartman
2021-09-14 18:07       ` Nick Desaulniers
2021-09-14 18:07         ` Nick Desaulniers
2021-09-14 18:12         ` Greg Kroah-Hartman
2021-09-14 17:32   ` [PATCH 5.10] " Kees Cook
2021-09-14 18:14     ` Linus Torvalds
2021-09-14 18:14       ` Linus Torvalds
2021-09-14 18:30       ` Linus Torvalds
2021-09-14 18:30         ` Linus Torvalds
2021-09-14 18:44         ` Nick Desaulniers
2021-09-14 18:44           ` Nick Desaulniers
2021-09-14 18:48           ` Linus Torvalds
2021-09-14 18:48             ` Linus Torvalds
2021-09-14 18:56             ` Linus Torvalds
2021-09-14 18:56               ` Linus Torvalds
2021-09-14 19:10               ` Nick Desaulniers
2021-09-14 19:10                 ` Nick Desaulniers
2021-09-14 19:45                 ` Linus Torvalds
2021-09-14 19:45                   ` Linus Torvalds
2021-09-14 19:50                   ` Nick Desaulniers [this message]
2021-09-14 19:50                     ` Nick Desaulniers
2021-09-14 19:57                     ` Linus Torvalds
2021-09-14 19:57                       ` Linus Torvalds
2021-09-14 18:47         ` Kees Cook
2021-09-14 18:54           ` Linus Torvalds
2021-09-14 18:54             ` Linus Torvalds
2021-09-14 19:12             ` Nick Desaulniers
2021-09-14 19:12               ` Nick Desaulniers
2021-09-14 19:52               ` Linus Torvalds
2021-09-14 19:52                 ` Linus Torvalds

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