linux-hardening - [PATCH v3] perf/x86/amd/uncore: Use kcalloc*() instead of kzalloc*()

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Date: Sat, 27 Apr 2024 18:45:23 +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>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	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>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Justin Stitt <justinstitt@...gle.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
Subject: [PATCH v3] perf/x86/amd/uncore: Use kcalloc*() instead of kzalloc*()

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

Here the multiplication is obviously safe. However, using kcalloc*()
is more appropriate [2] and improves readability. This patch has no
effect on runtime behavior.

Link: https://github.com/KSPP/linux/issues/162 [1]
Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2]
Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Signed-off-by: Erick Archer <erick.archer@...look.com>
---
Changes in v3:
- Update the commit message to better explain the changes.
- Rebase against linux-next.

Changes in v2:
- Add the "Reviewed-by:" tag.
- Rebase against linux-next.

Previous versions:
v1 -> https://lore.kernel.org/linux-hardening/20240116125813.3754-1-erick.archer@gmx.com
v2 -> https://lore.kernel.org/linux-hardening/AS8PR02MB7237A07D73D6D15EBF72FD8D8B392@AS8PR02MB7237.eurprd02.prod.outlook.com

Hi,

This is a new try. In the v2 version Ingo explained that this change
is nonsense since kzalloc() is a perfectly usable interface and there
is no real overflow here.

Anyway, if we have the 2-factor form of the allocator, I think it is
a good practice to use it.

In this version I have updated the commit message to explain that
the code is obviusly safe in contrast with the last version where the
impression was given that there was a real overlow bug.

I hope this patch can be applied this time.

Regards,
Erick
---
 arch/x86/events/amd/uncore.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index 4ccb8fa483e6..61c0a2114183 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -479,8 +479,8 @@ static int amd_uncore_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
 				goto fail;
 
 			curr->cpu = cpu;
-			curr->events = kzalloc_node(sizeof(*curr->events) *
-						    pmu->num_counters,
+			curr->events = kcalloc_node(pmu->num_counters,
+						    sizeof(*curr->events),
 						    GFP_KERNEL, node);
 			if (!curr->events) {
 				kfree(curr);
@@ -928,7 +928,7 @@ int amd_uncore_umc_ctx_init(struct amd_uncore *uncore, unsigned int cpu)
 		uncore->num_pmus += group_num_pmus[gid];
 	}
 
-	uncore->pmus = kzalloc(sizeof(*uncore->pmus) * uncore->num_pmus,
+	uncore->pmus = kcalloc(uncore->num_pmus, sizeof(*uncore->pmus),
 			       GFP_KERNEL);
 	if (!uncore->pmus) {
 		uncore->num_pmus = 0;
-- 
2.25.1