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San: Unguard guarded slabs during arena destruction

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When opt_retain is on, slab extents remain guarded in all states, even
retained. This works well if arena is never destroyed, because we
anticipate those slabs will be eventually reused. But if the arena is
destroyed, the slabs must be unguarded to prevent leaking guard pages.
This commit is contained in:
Alex Lapenkou 2021-11-02 15:56:36 -07:00 committed by Alexander Lapenkov
parent b6a7a535b3
commit 6cb585b13a
3 changed files with 42 additions and 10 deletions
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9
include/jemalloc/internal/guard.h
View File

@ -14,7 +14,14 @@ extern size_t opt_san_guard_large;
extern size_t opt_san_guard_small;
void guard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap);
void unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap);
void unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
emap_t *emap);
/*
* Unguard the extent, but don't modify emap boundaries. Must be called on an
* extent that has been erased from emap and shouldn't be placed back.
*/
void unguard_pages_pre_destroy(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
emap_t *emap);
void tsd_san_init(tsd_t *tsd);
static inline bool

8
src/extent.c
View File

@ -1057,12 +1057,14 @@ extent_destroy_wrapper(tsdn_t *tsdn, pac_t *pac, ehooks_t *ehooks,
edata_t *edata) {
assert(edata_base_get(edata) != NULL);
assert(edata_size_get(edata) != 0);
assert(edata_state_get(edata) == extent_state_retained);
assert(emap_edata_is_acquired(tsdn, pac->emap, edata));
witness_assert_depth_to_rank(tsdn_witness_tsdp_get(tsdn),
WITNESS_RANK_CORE, 0);
/* Deregister first to avoid a race with other allocating threads. */
extent_deregister(tsdn, pac, edata);
if (edata_guarded_get(edata)) {
unguard_pages_pre_destroy(tsdn, ehooks, edata, pac->emap);
}
edata_addr_set(edata, edata_base_get(edata));
/* Try to destroy; silently fail otherwise. */

35
src/guard.c
View File

@ -32,10 +32,16 @@ guard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
/* The new boundary will be registered on the pa_alloc path. */
}
void
unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
static void
unguard_pages_impl(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap,
bool reg_emap) {
/* Remove the inner boundary which no longer exists. */
emap_deregister_boundary(tsdn, emap, edata);
if (reg_emap) {
assert(edata_state_get(edata) == extent_state_active);
emap_deregister_boundary(tsdn, emap, edata);
} else {
assert(edata_state_get(edata) == extent_state_retained);
}
size_t size = edata_size_get(edata);
size_t size_with_guards = size + PAGE_GUARDS_SIZE;
@ -44,7 +50,6 @@ unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
uintptr_t guard1 = addr - PAGE;
uintptr_t guard2 = addr + size;
assert(edata_state_get(edata) == extent_state_active);
ehooks_unguard(tsdn, ehooks, (void *)guard1, (void *)guard2);
/* Update the true addr and usable size of the edata. */
@ -52,8 +57,26 @@ unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
edata_addr_set(edata, (void *)guard1);
edata_guarded_set(edata, false);
/* Then re-register the outer boundary including the guards. */
emap_register_boundary(tsdn, emap, edata, SC_NSIZES, /* slab */ false);
/*
* Then re-register the outer boundary including the guards, if
* requested.
*/
if (reg_emap) {
emap_register_boundary(tsdn, emap, edata, SC_NSIZES,
/* slab */ false);
}
}
void
unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
unguard_pages_impl(tsdn, ehooks, edata, emap, /* reg_emap */ true);
}
void
unguard_pages_pre_destroy(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
emap_t *emap) {
emap_assert_not_mapped(tsdn, emap, edata);
unguard_pages_impl(tsdn, ehooks, edata, emap, /* reg_emap */ false);
}
void