Re: [PATCH v2] selftests:mm: Fix mmap() error paths to check for MAP_FAILED

On 8/22/24 17:30, Yang Ruibin wrote:

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

Shouldn't you have written "avoid processing the return value from a failed mmap" instead of "avoid incorrectly handling a valid mapping", because !addr won't be a valid mapping? Also, I guess it would be better to use ksft_exit_fail_perror(), but I won't insist.

Signed-off-by: Yang Ruibin 11162571@vivo.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 b748c4890..dad54840f 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 ef7d911da..b89cb83ca 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 bdfa5d085..4ccbc053b 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);