linux-kernel - [PATCH v2] perf bench: Fix undefined behavior in cmpworker()

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250107073906.3323640-1-visitorckw@gmail.com>
Date: Tue,  7 Jan 2025 15:39:06 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org
Cc: mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	kan.liang@...ux.intel.com,
	Ching-Chun Huang <jserv@...s.ncku.edu.tw>,
	Chun-Ying Huang <chuang@...nycu.edu.tw>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Kuan-Wei Chiu <visitorckw@...il.com>,
	stable@...r.kernel.org
Subject: [PATCH v2] perf bench: Fix undefined behavior in cmpworker()

The comparison function cmpworker() violates the C standard's
requirements for qsort() comparison functions, which mandate symmetry
and transitivity:

Symmetry: If x < y, then y > x.
Transitivity: If x < y and y < z, then x < z.

In its current implementation, cmpworker() incorrectly returns 0 when
w1->tid < w2->tid, which breaks both symmetry and transitivity. This
violation causes undefined behavior, potentially leading to issues such
as memory corruption in 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@...r.kernel.org
Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
---
Changes in v2:
- Rewrite commit message

 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)
 
 	struct worker *w1 = (struct worker *) p1;
 	struct worker *w2 = (struct worker *) p2;
-	return w1->tid > w2->tid;
+	return w1->tid > w2->tid ? 1 : -1;
 }
 
 int bench_epoll_wait(int argc, const char **argv)
-- 
2.34.1