From: Erick Archer <erick.archer@outlook.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>,
Erick Archer <erick.archer@outlook.com>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
"Liang, Kan" <kan.liang@linux.intel.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Justin Stitt <justinstitt@google.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH] perf/ring_buffer: Prefer struct_size over open coded arithmetic
Date: Sat, 4 May 2024 19:21:48 +0200 [thread overview]
Message-ID: <AS8PR02MB7237E1240937477D0D6F57AB8B1E2@AS8PR02MB7237.eurprd02.prod.outlook.com> (raw)
In-Reply-To: <202405021552.5C000EA@keescook>
On Thu, May 02, 2024 at 03:55:36PM -0700, Kees Cook wrote:
> On Thu, May 02, 2024 at 11:18:37AM +0200, Peter Zijlstra wrote:
> > On Wed, May 01, 2024 at 01:21:42PM -0700, Kees Cook wrote:
> > > On Tue, Apr 30, 2024 at 11:15:04AM +0200, Peter Zijlstra wrote:
> > > > On Mon, Apr 29, 2024 at 07:40:58PM +0200, Erick Archer wrote:
> > > > > This is an effort to get rid of all multiplications from allocation
> > > > > functions in order to prevent integer overflows [1][2].
> > > >
> > > > So personally I detest struct_size() because I can never remember wtf it
> > > > does, whereas the code it replaces is simple and straight forward :/
> > >
> > > Sure, new APIs can involved a learning curve. If we can all handle
> > > container_of(), we can deal with struct_size(). :)
> >
> > containre_of() is actually *much* shorter than typing it all out. Which
> > is a benefit.
> >
> > struct_size() not so much. That's just obfuscation for obfuscation's
> > sake.
I do not agree with this.
>
> It's really not -- it's making sure that the calculation is semantically
> sane: all the right things are being used for the struct size calculation
> and things can't "drift", if types change, flex array changes, etc. It's
> both a code robustness improvement and a wrap-around stopping improvement.
>
Also, in the "Deprecated Interfaces, Language Features, Attributes, and
Conventions" [1] it says verbatim:
Another common case to avoid is calculating the size of a structure
with a trailing array of others structures, as in:
header = kzalloc(sizeof(*header) + count * sizeof(*header->item),
GFP_KERNEL);
Instead, use the helper:
header = kzalloc(struct_size(header, item, count), GFP_KERNEL);
Therefore, if there is a convention to follow, we should not make an
exception. Moreover, struct_size is widely used in the kernel and
widely accepted. Also makes the code safer.
So, I will send a new patch with the changes Kees proposed and I
hope that it will be the first step in the adoption of struct_size
in the perf and sched subsystems ;)
Regards,
Erick
[1] https://docs.kernel.org/process/deprecated.html
> --
> Kees Cook
prev parent reply other threads:[~2024-05-04 17:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-29 17:40 [PATCH] perf/ring_buffer: Prefer struct_size over open coded arithmetic Erick Archer
2024-04-29 18:23 ` Kees Cook
2024-04-30 9:15 ` Peter Zijlstra
2024-05-01 17:23 ` Erick Archer
2024-05-01 20:21 ` Kees Cook
2024-05-02 9:18 ` Peter Zijlstra
2024-05-02 22:55 ` Kees Cook
2024-05-04 17:21 ` Erick Archer [this message]
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