From: Hongfu Li <lihongfu@kylinos.cn>
Date: Wed, 13 May 2026 02:52:23 +0000 (+0800)
Subject: selftests/mm: fix incorrect mmap() error handling with NULL instead of MAP_FAILED
X-Git-Tag: v7.2-rc1~59^2~27
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a179686b917ca30232cb70eb4408d34d9de3814d;p=thirdparty%2Fkernel%2Flinux.git

selftests/mm: fix incorrect mmap() error handling with NULL instead of MAP_FAILED

mmap() returns MAP_FAILED, which is defined as (void *)-1, on error, not
NULL.  Several selftests incorrectly check the return value of mmap()
using !ptr or ptr == NULL, which would erroneously treat MAP_FAILED as a
valid pointer since MAP_FAILED is non-zero and non-NULL.  This can lead to
segfaults when mmap() actually fails under memory pressure.

Link: https://lore.kernel.org/20260513025223.592766-1-lihongfu@kylinos.cn
Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
index 64d1c63ae8c07..a050f4840cfa3 100644
--- a/tools/testing/selftests/mm/ksm_tests.c
+++ b/tools/testing/selftests/mm/ksm_tests.c
@@ -174,7 +174,7 @@ 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) {
 		ksft_perror("mmap");
 		return NULL;
 	}
diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c
index 88050e0f829a0..7fce5d0b622be 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 c426c4636ef57..fb1864a68e1c6 100644
--- a/tools/testing/selftests/mm/soft-dirty.c
+++ b/tools/testing/selftests/mm/soft-dirty.c
@@ -143,7 +143,7 @@ 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);
@@ -155,7 +155,7 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon)
 		ftruncate(test_fd, pagesize);
 		map = mmap(NULL, pagesize, PROT_READ|PROT_WRITE,
 			   MAP_SHARED, test_fd, 0);
-		if (!map)
+		if (map == MAP_FAILED)
 			ksft_exit_fail_msg("file mmap failed\n");
 	}
 
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 336a26751d3fa..311fc5b4513eb 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -396,7 +396,7 @@ bool softdirty_supported(void)
 	/* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */
 	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");
 
 	supported = check_vmflag(addr, "sd");