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Wed, 13 May 2026 01:55:02 -0700 (PDT) Date: Wed, 13 May 2026 08:55:01 +0000 From: Wei Yang To: Hongfu Li Cc: shuah@kernel.org, akpm@linux-foundation.org, reddybalavignesh9979@gmail.com, richard.weiyang@gmail.com, mic@digikod.net, sj@kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests/perf_events: Fix mmap() error check in sigtrap_threads Message-ID: <20260513085501.lzljqdgzwanbqtr4@master> Reply-To: Wei Yang References: <20260513025838.594945-1-lihongfu@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260513025838.594945-1-lihongfu@kylinos.cn> User-Agent: NeoMutt/20170113 (1.7.2) On Wed, May 13, 2026 at 10:58:38AM +0800, Hongfu Li wrote: >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. > >Signed-off-by: Hongfu Li Ah, looks you are right. Reviewed-by: Wei Yang >--- > tools/testing/selftests/perf_events/watermark_signal.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/tools/testing/selftests/perf_events/watermark_signal.c b/tools/testing/selftests/perf_events/watermark_signal.c >index 0f64b9b17081..a84709cabd8b 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; > } >-- >2.25.1 -- Wei Yang Help you, Help me