linux-hardening - Re: [PATCH] perf/x86/amd/uncore: Add flex array to struct amd_uncore

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Date: Sat, 11 May 2024 13:04:51 -0700
From: Kees Cook <keescook@...omium.org>
To: Erick Archer <erick.archer@...look.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Justin Stitt <justinstitt@...gle.com>, x86@...nel.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] perf/x86/amd/uncore: Add flex array to struct
 amd_uncore_ctx

On Sat, May 11, 2024 at 04:51:54PM +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].
> 
> The "struct amd_uncore_ctx" can be refactored to use a flex array for
> the "events" member. This way, the allocation/freeing of the memory can
> be simplified.
> 
> Specifically, as the "curr" variable is a pointer to the amd_uncore_ctx
> structure and it now ends up in a flexible array:
> 
> struct amd_uncore_ctx {
>         [...]
>         struct perf_event *events[];
> };
> 
> the two-step allocation can be simplifief by using just one kzalloc_node
> function and the struct_size() helper to do the arithmetic calculation
> for the memory to be allocated.
> 
> This way, the code is more readable and safer.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Suggested-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> Signed-off-by: Erick Archer <erick.archer@...look.com>
> ---
> Hi,
> 
> This patch can be considered v4 of this other one [1]. However, since
> the patch has completely changed due to the addition of the flex array,
> I have decided to make a new series and remove the "Reviewed-by:" tag
> by Gustavo A. R. Silva and Kees cook.
> 
> [1] https://lore.kernel.org/linux-hardening/PAXPR02MB7248F46DEFA47E79677481B18B152@PAXPR02MB7248.eurprd02.prod.outlook.com/
> 
> Thanks,
> Erick
> ---
>  arch/x86/events/amd/uncore.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)

My favorite kind of patch: fewer lines, clearer code.

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook