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[sanitizer] Make sure libmalloc doesn't remove the sanitizer zone from malloc_zones[0] 

In certain OS versions, it was possible that libmalloc replaced the sanitizer zone from being the default zone (i.e. being in malloc_zones[0]). This patch introduces a failsafe that makes sure we always stay the default zone. No testcase for this, because this doesn't reproduce under normal circumstances.

Differential Revision: https://reviews.llvm.org/D27083

llvm-svn: 289376
This commit is contained in:
Kuba Mracek 2016-12-11 08:45:36 +00:00
parent b93f78128f
commit 1c002267fb
1 changed files with 23 additions and 0 deletions
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23
compiler-rt/lib/sanitizer_common/sanitizer_malloc_mac.inc
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@ -62,6 +62,29 @@ INTERCEPTOR(void, malloc_destroy_zone, malloc_zone_t *zone) {
COMMON_MALLOC_FREE(zone);
}
extern unsigned malloc_num_zones;
extern malloc_zone_t **malloc_zones;
// We need to make sure that sanitizer_zone is registered as malloc_zones[0]. If
// libmalloc tries to set up a different zone as malloc_zones[0], it will call
// mprotect(malloc_zones, ..., PROT_READ). This interceptor will catch that and
// make sure we are still the first (default) zone.
INTERCEPTOR(int, mprotect, void *addr, size_t len, int prot) {
if (addr == malloc_zones && prot == PROT_READ) {
if (malloc_num_zones > 1 && malloc_zones[0] != &sanitizer_zone) {
for (unsigned i = 1; i < malloc_num_zones; i++) {
if (malloc_zones[i] == &sanitizer_zone) {
// Swap malloc_zones[0] and malloc_zones[i].
malloc_zones[i] = malloc_zones[0];
malloc_zones[0] = &sanitizer_zone;
break;
}
}
}
}
return REAL(mprotect)(addr, len, prot);
}
INTERCEPTOR(malloc_zone_t *, malloc_default_zone, void) {
COMMON_MALLOC_ENTER();
return &sanitizer_zone;