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From: Erick Archer <erick.archer@gmx.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
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	Ian Rogers <irogers@google.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Kees Cook <keescook@chromium.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Erick Archer <erick.archer@gmx.com>,
	x86@kernel.org,
	linux-perf-users@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH] perf/x86/rapl: Prefer struct_size over open coded arithmetic
Date: Sun, 17 Mar 2024 17:44:42 +0100
Message-Id: <20240317164442.6729-1-erick.archer@gmx.com>
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This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

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

struct rapl_pmus {
	[...]
	struct rapl_pmu *pmus[] __counted_by(maxdie);
};

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() function.

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]
Signed-off-by: Erick Archer <erick.archer@gmx.com>
=2D--
 arch/x86/events/rapl.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c
index fb2b1961e5a3..8ef08b5d55a7 100644
=2D-- a/arch/x86/events/rapl.c
+++ b/arch/x86/events/rapl.c
@@ -675,10 +675,8 @@ static const struct attribute_group *rapl_attr_update=
[] =3D {
 static int __init init_rapl_pmus(void)
 {
 	int maxdie =3D topology_max_packages() * topology_max_dies_per_package()=
;
-	size_t size;

-	size =3D sizeof(*rapl_pmus) + maxdie * sizeof(struct rapl_pmu *);
-	rapl_pmus =3D kzalloc(size, GFP_KERNEL);
+	rapl_pmus =3D kzalloc(struct_size(rapl_pmus, pmus, maxdie), GFP_KERNEL);
 	if (!rapl_pmus)
 		return -ENOMEM;

=2D-
2.25.1