From: Hongfu Li <lihongfu@kylinos.cn>
Date: Wed, 13 May 2026 02:58:38 +0000 (+0800)
Subject: selftests/perf_events: fix mmap() error check in sigtrap_threads
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2f5026b8d4fe34601d692ae7f7cd27367e002266;p=thirdparty%2Flinux.git

selftests/perf_events: fix mmap() error check in sigtrap_threads

In sigtrap_threads(), the return value of mmap() is checked against NULL.
mmap() returns MAP_FAILED, which is (void *)-1, not NULL, when it fails.
Since MAP_FAILED is non-zero and non-NULL, the condition "p == NULL" will
never be true on failure, causing the program to proceed with an invalid
pointer and segfault if mmap() actually fails under memory pressure.

Link: https://lore.kernel.org/20260513025838.594945-1-lihongfu@kylinos.cn
Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mickael Salaun <mic@digikod.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Kyle Huey <khuey@kylehuey.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/tools/testing/selftests/perf_events/watermark_signal.c b/tools/testing/selftests/perf_events/watermark_signal.c
index 0f64b9b170813..a84709cabd8be 100644
--- a/tools/testing/selftests/perf_events/watermark_signal.c
+++ b/tools/testing/selftests/perf_events/watermark_signal.c
@@ -102,7 +102,7 @@ TEST(watermark_signal)
 	}
 
 	p = mmap(NULL, 2 * page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-	if (p == NULL) {
+	if (p == MAP_FAILED) {
 		perror("mmap");
 		goto cleanup;
 	}