linux-kernel - [PATCH v4 2/3] perf/x86/intel/uncore: Prefer struct

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Message-ID:
 <AS8PR02MB72374D446ECC6BD0711A51DC8BFD2@AS8PR02MB7237.eurprd02.prod.outlook.com>
Date: Sat,  1 Jun 2024 18:56:17 +0200
From: Erick Archer <erick.archer@...look.com>
To: 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>,
	Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Matthew Wilcox <mawilcox@...rosoft.com>
Cc: Erick Archer <erick.archer@...look.com>,
	x86@...nel.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH v4 2/3] perf/x86/intel/uncore: Prefer struct_size over open coded arithmetic

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

As the "box" variable is a pointer to "struct intel_uncore_box" and
this structure ends in a flexible array:

struct intel_uncore_box {
	[...]
	struct intel_uncore_extra_reg shared_regs[];
};

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() function.

This way, the code is more readable and 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]
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Erick Archer <erick.archer@...look.com>
---
 arch/x86/events/intel/uncore.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index 419c517b8594..b0d518d752aa 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -350,12 +350,11 @@ static void uncore_pmu_init_hrtimer(struct intel_uncore_box *box)
 static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,
 						 int node)
 {
-	int i, size, numshared = type->num_shared_regs ;
+	int i, numshared = type->num_shared_regs;
 	struct intel_uncore_box *box;
 
-	size = sizeof(*box) + numshared * sizeof(struct intel_uncore_extra_reg);
-
-	box = kzalloc_node(size, GFP_KERNEL, node);
+	box = kzalloc_node(struct_size(box, shared_regs, numshared), GFP_KERNEL,
+			   node);
 	if (!box)
 		return NULL;
 
-- 
2.25.1