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Add dummy implementations for most remaining OSX zone allocator funct…
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…ions

Some system libraries are using malloc_default_zone() and then using
some of the malloc_zone_* API. Under normal conditions, those functions
check the malloc_zone_t/malloc_introspection_t struct for the values
that are allowed to be NULL, so that a NULL deref doesn't happen.

As of OSX 10.12, malloc_default_zone() doesn't return the actual default
zone anymore, but returns a fake, wrapper zone. The wrapper zone defines
all the possible functions in the malloc_zone_t/malloc_introspection_t
struct (almost), and calls the function from the registered default zone
(jemalloc in our case) on its own. Without checking whether the pointers
are NULL.

This means that a system library that calls e.g.
malloc_zone_batch_malloc(malloc_default_zone(), ...) ends up trying to
call jemalloc_zone.batch_malloc, which is NULL, and crash follows.

So as of OSX 10.12, the default zone is required to have all the
functions available (really, the same as the wrapper zone), even if they
do nothing.

This is arguably a bug in libsystem_malloc in OSX 10.12, but jemalloc
still needs to work in that case.
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@glandium
glandium committed Jan 18, 2017
1 parent d5a6ab5 commit 62d87fc
Showing 1 changed file with 108 additions and 10 deletions.
118 changes: 108 additions & 10 deletions src/zone.c
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Original file line number Diff line number Diff line change
Expand Up @@ -100,9 +100,24 @@ static void *zone_memalign(malloc_zone_t *zone, size_t alignment,
static void zone_free_definite_size(malloc_zone_t *zone, void *ptr,
size_t size);
static void zone_destroy(malloc_zone_t *zone);
static unsigned zone_batch_malloc(struct _malloc_zone_t *zone, size_t size,
void **results, unsigned num_requested);
static void zone_batch_free(struct _malloc_zone_t *zone,
void **to_be_freed, unsigned num_to_be_freed);
static size_t zone_pressure_relief(struct _malloc_zone_t *zone, size_t goal);
static size_t zone_good_size(malloc_zone_t *zone, size_t size);
static kern_return_t zone_enumerator(task_t task, void *data, unsigned type_mask,
vm_address_t zone_address, memory_reader_t reader,
vm_range_recorder_t recorder);
static boolean_t zone_check(malloc_zone_t *zone);
static void zone_print(malloc_zone_t *zone, boolean_t verbose);
static void zone_log(malloc_zone_t *zone, void *address);
static void zone_force_lock(malloc_zone_t *zone);
static void zone_force_unlock(malloc_zone_t *zone);
static void zone_statistics(malloc_zone_t *zone,
malloc_statistics_t *stats);
static boolean_t zone_locked(malloc_zone_t *zone);
static void zone_reinit_lock(malloc_zone_t *zone);

/******************************************************************************/
/*
Expand Down Expand Up @@ -204,6 +219,39 @@ zone_destroy(malloc_zone_t *zone)
not_reached();
}

static unsigned
zone_batch_malloc(struct _malloc_zone_t *zone, size_t size, void **results,
unsigned num_requested)
{
unsigned i;

for (i = 0; i < num_requested; i++) {
results[i] = je_malloc(size);
if (!results[i])
break;
}

return i;
}

static void
zone_batch_free(struct _malloc_zone_t *zone, void **to_be_freed,
unsigned num_to_be_freed)
{
unsigned i;

for (i = 0; i < num_to_be_freed; i++) {
zone_free(zone, to_be_freed[i]);
to_be_freed[i] = NULL;
}
}

static size_t
zone_pressure_relief(struct _malloc_zone_t *zone, size_t goal)
{
return 0;
}

static size_t
zone_good_size(malloc_zone_t *zone, size_t size)
{
Expand All @@ -213,6 +261,30 @@ zone_good_size(malloc_zone_t *zone, size_t size)
return (s2u(size));
}

static kern_return_t
zone_enumerator(task_t task, void *data, unsigned type_mask,
vm_address_t zone_address, memory_reader_t reader,
vm_range_recorder_t recorder)
{
return KERN_SUCCESS;
}

static boolean_t
zone_check(malloc_zone_t *zone)
{
return true;
}

static void
zone_print(malloc_zone_t *zone, boolean_t verbose)
{
}

static void
zone_log(malloc_zone_t *zone, void *address)
{
}

static void
zone_force_lock(malloc_zone_t *zone)
{
Expand All @@ -236,6 +308,31 @@ zone_force_unlock(malloc_zone_t *zone)
jemalloc_postfork_child();
}

static void
zone_statistics(malloc_zone_t *zone, malloc_statistics_t *stats)
{
/* We make no effort to actually fill the values */
stats->blocks_in_use = 0;
stats->size_in_use = 0;
stats->max_size_in_use = 0;
stats->size_allocated = 0;
}

static boolean_t
zone_locked(malloc_zone_t *zone)
{
/* Pretend no lock is being held */
return false;
}

static void
zone_reinit_lock(malloc_zone_t *zone)
{
/* As of OSX 10.12, this function is only used when force_unlock would
* be used if the zone version were < 9. So just use force_unlock. */
zone_force_unlock(zone);
}

static void
zone_init(void)
{
Expand All @@ -248,23 +345,23 @@ zone_init(void)
jemalloc_zone.realloc = zone_realloc;
jemalloc_zone.destroy = zone_destroy;
jemalloc_zone.zone_name = "jemalloc_zone";
jemalloc_zone.batch_malloc = NULL;
jemalloc_zone.batch_free = NULL;
jemalloc_zone.batch_malloc = zone_batch_malloc;
jemalloc_zone.batch_free = zone_batch_free;
jemalloc_zone.introspect = &jemalloc_zone_introspect;
jemalloc_zone.version = 8;
jemalloc_zone.version = 9;
jemalloc_zone.memalign = zone_memalign;
jemalloc_zone.free_definite_size = zone_free_definite_size;
jemalloc_zone.pressure_relief = NULL;
jemalloc_zone.pressure_relief = zone_pressure_relief;

jemalloc_zone_introspect.enumerator = NULL;
jemalloc_zone_introspect.enumerator = zone_enumerator;
jemalloc_zone_introspect.good_size = zone_good_size;
jemalloc_zone_introspect.check = NULL;
jemalloc_zone_introspect.print = NULL;
jemalloc_zone_introspect.log = NULL;
jemalloc_zone_introspect.check = zone_check;
jemalloc_zone_introspect.print = zone_print;
jemalloc_zone_introspect.log = zone_log;
jemalloc_zone_introspect.force_lock = zone_force_lock;
jemalloc_zone_introspect.force_unlock = zone_force_unlock;
jemalloc_zone_introspect.statistics = NULL;
jemalloc_zone_introspect.zone_locked = NULL;
jemalloc_zone_introspect.statistics = zone_statistics;
jemalloc_zone_introspect.zone_locked = zone_locked;
jemalloc_zone_introspect.enable_discharge_checking = NULL;
jemalloc_zone_introspect.disable_discharge_checking = NULL;
jemalloc_zone_introspect.discharge = NULL;
Expand All @@ -273,6 +370,7 @@ zone_init(void)
#else
jemalloc_zone_introspect.enumerate_unavailable_without_blocks = NULL;
#endif
jemalloc_zone_introspect.reinit_lock = zone_reinit_lock;
}

static malloc_zone_t *
Expand Down

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