From: Kees Cook <keescook@chromium.org>
To: Erick Archer <erick.archer@outlook.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
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>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v3] perf/ring_buffer: Prefer struct_size over open coded arithmetic
Date: Mon, 13 May 2024 12:45:04 -0700 [thread overview]
Message-ID: <202405131245.E572E4C6@keescook> (raw)
In-Reply-To: <AS8PR02MB72379B4807F3951A1B926BA58BE02@AS8PR02MB7237.eurprd02.prod.outlook.com>
On Sat, May 11, 2024 at 03:24:37PM +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].
>
> As the "rb" variable is a pointer to "struct perf_buffer" and this
> structure ends in a flexible array:
>
> struct perf_buffer {
> [...]
> void *data_pages[];
> };
>
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the calculation "size + count * size" in
> the kzalloc_node() functions.
>
> In the "rb_alloc" function defined in the else branch of the macro
>
> #ifndef CONFIG_PERF_USE_VMALLOC
>
> the count in the struct_size helper is the literal "1" since only one
> pointer to void is allocated. Also, remove the "size" variable as it
> is no longer needed.
>
> At the same time, prepare for the coming implementation by GCC and Clang
> of the __counted_by attribute. Flexible array members annotated with
> __counted_by can have their accesses bounds-checked at run-time via
> CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
> strcpy/memcpy-family functions). In this case, it is important to note
> that the logic needs a little refactoring to ensure that the "nr_pages"
> member is initialized before the first access to the flex array.
>
> In one case, it is only necessary to move the "nr_pages" assignment
> before the array-writing loop while in the other case the access to the
> flex array needs to be moved inside the if branch and after the
> "nr_pages" assignment.
>
> This way, the code is more safer.
>
> This code was detected with the help of Coccinelle, and audited and
> modified manually.
>
> 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]
> Signed-off-by: Erick Archer <erick.archer@outlook.com>
Thanks!
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
prev parent reply other threads:[~2024-05-13 19:45 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-11 13:24 [PATCH v3] perf/ring_buffer: Prefer struct_size over open coded arithmetic Erick Archer
2024-05-13 19:45 ` Kees Cook [this message]
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