linux-kernel - [PATCH v1] tools:mm:Check mmap based on return values

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Message-Id: <20240821035005.4423-1-11162571@vivo.com>
Date: Tue, 20 Aug 2024 23:50:03 -0400
From: Yang Ruibin <11162571@...o.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Shuah Khan <shuah@...nel.org>,
	linux-mm@...ck.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: opensource.kernel@...o.com,
	Yang Ruibin <11162571@...o.com>
Subject: [PATCH v1] tools:mm:Check mmap based on return values

To correctly detect whether mmap is successful, must use if 
(map_ptr == MAP_FAILED)to avoid incorrectly handling a valid mapping.

Signed-off-by: Yang Ruibin <11162571@...o.com>
---
 tools/testing/selftests/mm/ksm_tests.c     | 2 +-
 tools/testing/selftests/mm/madv_populate.c | 2 +-
 tools/testing/selftests/mm/soft-dirty.c    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
index b748c48908d9..dad54840f32e 100644
--- a/tools/testing/selftests/mm/ksm_tests.c
+++ b/tools/testing/selftests/mm/ksm_tests.c
@@ -201,7 +201,7 @@ static void  *allocate_memory(void *ptr, int prot, int mapping, char data, size_
 {
 	void *map_ptr = mmap(ptr, map_size, PROT_WRITE, mapping, -1, 0);
 
-	if (!map_ptr) {
+	if (map_ptr == MAP_FAILED) {
 		perror("mmap");
 		return NULL;
 	}
diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c
index ef7d911da13e..b89cb83ca5c5 100644
--- a/tools/testing/selftests/mm/madv_populate.c
+++ b/tools/testing/selftests/mm/madv_populate.c
@@ -34,7 +34,7 @@ static void sense_support(void)
 
 	addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,
 		    MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
-	if (!addr)
+	if (addr == MAP_FAILED)
 		ksft_exit_fail_msg("mmap failed\n");
 
 	ret = madvise(addr, pagesize, MADV_POPULATE_READ);
diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c
index bdfa5d085f00..4ccbc053bcce 100644
--- a/tools/testing/selftests/mm/soft-dirty.c
+++ b/tools/testing/selftests/mm/soft-dirty.c
@@ -134,7 +134,7 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon)
 	if (anon) {
 		map = mmap(NULL, pagesize, PROT_READ|PROT_WRITE,
 			   MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
-		if (!map)
+		if (map == MAP_FAILED)
 			ksft_exit_fail_msg("anon mmap failed\n");
 	} else {
 		test_fd = open(fname, O_RDWR | O_CREAT, 0664);
-- 
2.34.1