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

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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>
This commit is contained in:
Hongfu Li 2026-05-13 10:52:23 +08:00 committed by Andrew Morton
parent b89a641056
commit a179686b91
4 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/testing/selftests/mm/ksm_tests.c
View File

@ -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;
}

2
tools/testing/selftests/mm/madv_populate.c
View File

@ -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);

4
tools/testing/selftests/mm/soft-dirty.c
View File

@ -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");
}

2
tools/testing/selftests/mm/vm_util.c
View File

@ -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");