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([140.113.216.168]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-725cab713c0sm4565464b3a.33.2024.12.09.06.57.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Dec 2024 06:57:35 -0800 (PST) From: Kuan-Wei Chiu To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org Cc: mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, jserv@ccns.ncku.edu.tw, chuang@cs.nycu.edu.tw, dave@stgolabs.net, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Kuan-Wei Chiu , stable@vger.kernel.org Subject: [PATCH] perf bench: Fix undefined behavior in cmpworker() Date: Mon, 9 Dec 2024 22:57:28 +0800 Message-Id: <20241209145728.1975311-1-visitorckw@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The comparison function cmpworker() does not comply with the C standard's requirements for qsort() comparison functions. Specifically, it returns 0 when w1->tid < w2->tid, which is incorrect. According to the standard, the function must return a negative value in such cases to preserve proper ordering. This violation causes undefined behavior, potentially leading to issues such as memory corruption in certain versions of glibc [1]. Fix the issue by returning -1 when w1->tid < w2->tid, ensuring compliance with the C standard and preventing undefined behavior. Link: https://www.qualys.com/2024/01/30/qsort.txt [1] Fixes: 121dd9ea0116 ("perf bench: Add epoll parallel epoll_wait benchmark") Cc: stable@vger.kernel.org Signed-off-by: Kuan-Wei Chiu --- tools/perf/bench/epoll-wait.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/bench/epoll-wait.c b/tools/perf/bench/epoll-wait.c index ef5c4257844d..4868d610e9bf 100644 --- a/tools/perf/bench/epoll-wait.c +++ b/tools/perf/bench/epoll-wait.c @@ -420,7 +420,7 @@ static int cmpworker(const void *p1, const void *p2) =20 struct worker *w1 =3D (struct worker *) p1; struct worker *w2 =3D (struct worker *) p2; - return w1->tid > w2->tid; + return w1->tid > w2->tid ? 1 : -1; } =20 int bench_epoll_wait(int argc, const char **argv) --=20 2.34.1