From: Mark Rutland <mark.rutland@arm.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
peterz@infradead.org, mingo@redhat.com, will.deacon@arm.com,
akpm@linux-foundation.org, kasan-dev@googlegroups.com,
linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] asm-generic, x86: wrap atomic operations
Date: Tue, 21 Mar 2017 10:41:39 +0000 [thread overview]
Message-ID: <20170321104139.GA22188@leverpostej> (raw)
In-Reply-To: <956a8e10-e03f-a21c-99d9-8a75c2616e0a@virtuozzo.com>
On Tue, Mar 21, 2017 at 12:25:06PM +0300, Andrey Ryabinin wrote:
> On 03/20/2017 08:17 PM, Mark Rutland wrote:
> > Hi,
> >
> > On Tue, Mar 14, 2017 at 08:24:13PM +0100, Dmitry Vyukov wrote:
> >> /**
> >> - * atomic_read - read atomic variable
> >> + * arch_atomic_read - read atomic variable
> >> * @v: pointer of type atomic_t
> >> *
> >> * Atomically reads the value of @v.
> >> */
> >> -static __always_inline int atomic_read(const atomic_t *v)
> >> +static __always_inline int arch_atomic_read(const atomic_t *v)
> >> {
> >> - return READ_ONCE((v)->counter);
> >> + /*
> >> + * We use READ_ONCE_NOCHECK() because atomic_read() contains KASAN
> >> + * instrumentation. Double instrumentation is unnecessary.
> >> + */
> >> + return READ_ONCE_NOCHECK((v)->counter);
> >> }
> >
> > Just to check, we do this to avoid duplicate reports, right?
> >
> > If so, double instrumentation isn't solely "unnecessary"; it has a
> > functional difference, and we should explicitly describe that in the
> > comment.
> >
> > ... or are duplicate reports supressed somehow?
>
> They are not suppressed yet. But I think we should just switch kasan
> to single shot mode, i.e. report only the first error. Single bug
> quite often has multiple invalid memory accesses causing storm in
> dmesg. Also write OOB might corrupt metadata so the next report will
> print bogus alloc/free stacktraces.
> In most cases we need to look only at the first report, so reporting
> anything after the first is just counterproductive.
FWIW, that sounds sane to me.
Given that, I agree with your comment regarding READ_ONCE{,_NOCHECK}().
If anyone really wants all the reports, we could have a boot-time option
to do that.
Thanks,
Mark.
next prev parent reply other threads:[~2017-03-21 10:42 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-14 19:24 [PATCH 0/3] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov
2017-03-14 19:24 ` [PATCH 1/3] kasan: allow kasan_check_read/write() to accept pointers to volatiles Dmitry Vyukov
2017-03-14 19:24 ` [PATCH 2/3] asm-generic, x86: wrap atomic operations Dmitry Vyukov
2017-03-20 16:41 ` Andrey Ryabinin
2017-03-20 17:17 ` Mark Rutland
2017-03-21 9:25 ` Andrey Ryabinin
2017-03-21 10:41 ` Mark Rutland [this message]
2017-03-21 18:06 ` Dmitry Vyukov
2017-03-21 21:20 ` Arnd Bergmann
2017-03-22 10:42 ` Dmitry Vyukov
2017-03-22 11:30 ` Arnd Bergmann
2017-03-22 12:14 ` Dmitry Vyukov
2017-03-22 12:48 ` Arnd Bergmann
2017-03-24 6:52 ` Ingo Molnar
2017-03-24 7:14 ` Dmitry Vyukov
2017-03-24 8:39 ` Dmitry Vyukov
2017-03-24 10:57 ` Ingo Molnar
2017-03-24 12:46 ` Dmitry Vyukov
2017-03-28 7:52 ` Ingo Molnar
2017-03-28 9:27 ` Peter Zijlstra
2017-03-28 9:46 ` Dmitry Vyukov
2017-03-28 9:51 ` Ingo Molnar
2017-03-28 9:56 ` Dmitry Vyukov
2017-03-28 10:15 ` Ingo Molnar
2017-03-28 16:29 ` Dmitry Vyukov
2017-03-14 19:24 ` [PATCH 3/3] asm-generic: add KASAN instrumentation to " Dmitry Vyukov
2017-03-30 22:30 ` [PATCH 0/3] x86, kasan: add KASAN checks " Andrew Morton
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=20170321104139.GA22188@leverpostej \
--to=mark.rutland@arm.com \
--cc=akpm@linux-foundation.org \
--cc=aryabinin@virtuozzo.com \
--cc=dvyukov@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=will.deacon@arm.com \
--cc=x86@kernel.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).