[3.12] gh-113343: Fix error check on mmap(2) (GH-113342) (#113374)

gh-113343: Fix error check on mmap(2) (GH-113342)

Fix error check on mmap(2)

It should check MAP_FAILED instead of NULL for error.

On mmap(2) man page:

  RETURN VALUE
       On success, mmap() returns a pointer to the mapped area.
       On error, the value MAP_FAILED (that is, (void *) -1) is
       returned, and errno is set to indicate the error.
(cherry picked from commit 6b70c3dc5ab2f290fcdbe474bcb7d6fdf29eae4c)

Co-authored-by: Namhyung Kim <namhyung@gmail.com>

diff --git a/Python/perf_trampoline.c b/Python/perf_trampoline.c
index a91f4f82877b3a5adaa9dbb02131d5a452efbd5b..ea9dc83dd0fd8a52495c3caf86dc66997a6c0605 100644 (file)
--- a/Python/perf_trampoline.c
+++ b/Python/perf_trampoline.c
@@ -247,7 +247,7 @@ new_code_arena(void)
              mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,
              -1,  // fd (not used here)
              0);  // offset (not used here)
-    if (!memory) {
+    if (memory == MAP_FAILED) {
         PyErr_SetFromErrno(PyExc_OSError);
         _PyErr_WriteUnraisableMsg(
             "Failed to create new mmap for perf trampoline", NULL);