From: Steven Rostedt <rostedt@goodmis.org>
To: Gavin Shan <gshan@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
shan.gavin@gmail.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64/mm: Reject invalid NUMA option
Date: Mon, 27 Apr 2020 22:59:44 -0400 [thread overview]
Message-ID: <20200427225944.185d4431@gandalf.local.home> (raw)
In-Reply-To: <20200427225406.7cacc796@gandalf.local.home>
On Mon, 27 Apr 2020 22:54:06 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 28 Apr 2020 10:59:14 +1000
> Gavin Shan <gshan@redhat.com> wrote:
>
> > Hi Mark,
> >
> > On 4/24/20 8:11 PM, Mark Rutland wrote:
> > > [Adding Steve, who added str_has_prefix()]
> > >
> > > On Fri, Apr 24, 2020 at 02:53:14PM +1000, Gavin Shan wrote:
> > >> The NUMA option is parsed by str_has_prefix() and the invalid option
> > >> like "numa=o" can be regarded as "numa=off" wrongly.
> > >
> > > Are you certain that can pass? If that can happen, str_has_prefix() is
> > > misnamed and does not seem to do what its kerneldoc says it does, as
> > > "off" is not a prefix of "o".
> > >
> >
> > Yes, It's possible. str_has_prefix() depends on strncmp(). In this particular
> > case, it's equal to the snippet of code as below: strncmp() returns zero.
> > str_has_prefix() returns 3.
>
> Wait! strncmp("o", "off", 3) returns zero?
>
> That to me looks like a bug!
>
> This means str_has_prefix() is broken in other areas as well.
>
>
> >
> > int strncmp(const char *cs, const char *ct, size_t count)
> > {
> > unsigned char c1, c2;
> >
> > while (count) {
> > c1 = *cs++;
> > c2 = *ct++;
> > if (c1 != c2)
> > return c1 < c2 ? -1 : 1;
> > if (!c1) /* break after first character is compared */
>
> Crap! That is totally wrong!
Looking at this again, it's not wrong. But how did we get here if c2 isn't
zero as well?
-- Steve
next prev parent reply other threads:[~2020-04-28 2:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 4:53 [PATCH] arm64/mm: Reject invalid NUMA option Gavin Shan
2020-04-24 10:11 ` Mark Rutland
2020-04-28 0:59 ` Gavin Shan
2020-04-28 2:54 ` Steven Rostedt
2020-04-28 2:59 ` Steven Rostedt [this message]
2020-04-28 3:09 ` Steven Rostedt
2020-04-28 4:35 ` Gavin Shan
2020-04-28 7:25 ` Will Deacon
2020-04-28 8:56 ` Gavin Shan
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