On Mon, Aug 1, 2022 at 8:15 PM Ruediger Pluem <[email protected]> wrote:
>
> On 8/1/22 5:05 PM, Ivan Zhakov wrote:
> >
> > My overall concern is that with the current solution as of r1902858, there
> > are valid and
> > reasonable allocation patterns that will cause an unbounded memory usage.
> >
> > For example, nothing prevents current or future PCRE versions from doing
> > this:
> >
> > for (int i = 0; i < N; i++)
> > {
> > void *p = private_malloc();
> > private_free(p);
> > }
> >
> > which is going to cause an unbounded memory usage because private_free() is
> > a no-op and retains everything that was allocated.
>
> This is true, but these kind of allocation patterns would also cause a lot of
> problems with a malloc/free backend and thus I think
> they are unlikely and would need to be addressed within PCRE. But even if
> they are happening and cannot be fixed for our users
> by adjusting PCRE e.g. because they are stuck to distribution versions we
> still could tackle this then with an apr_bucket_alloc /
> apr_bucket_free approach or worst case even with a malloc / free approach for
> particular "bad" PCRE versions. But for now the
> current code seems to work well with the current PCRE allocation pattern.
We could switch to an apr_allocator+apr_memnode_t pattern just now,
and trade the 8K used by the current (sub)pool for an overhead of
sizeof(apr_memnode_t)+8 only, and private_free() just calls
apr_allocator_free().
Something like the attached patch?
Regards;
Yann.
Index: server/util_pcre.c
===================================================================
--- server/util_pcre.c (revision 1902909)
+++ server/util_pcre.c (working copy)
@@ -294,7 +294,17 @@ typedef int* match_vector_pt;
#endif
#if APREG_USE_THREAD_LOCAL
-static AP_THREAD_LOCAL apr_pool_t *thread_pool;
+#include "mpm_common.h" /* for ap_max_mem_free */
+
+static AP_THREAD_LOCAL apr_allocator_t *thread_alloc;
+static apr_status_t destroy_thread_alloc(void *alloc)
+{
+ apr_allocator_destroy(alloc);
+ return APR_SUCCESS;
+}
+
+/* Alignment for the apr_memnode_t pointer saved by each allocation */
+#define SIZEOF_VOIDP_ALIGNED APR_ALIGN_DEFAULT(APR_SIZEOF_VOIDP)
#endif
struct match_data_state {
@@ -303,8 +313,8 @@ struct match_data_state {
apr_size_t buf_used;
#if APREG_USE_THREAD_LOCAL
- apr_thread_t *thd;
- apr_pool_t *pool;
+ apr_pool_t *tp;
+ apr_allocator_t *ta;
#endif
#ifdef HAVE_PCRE2
@@ -326,17 +336,36 @@ static void * private_malloc(size_t size, void *ct
}
#if APREG_USE_THREAD_LOCAL
- if (state->thd) {
- apr_pool_t *pool = state->pool;
- if (pool == NULL) {
- pool = thread_pool;
- if (pool == NULL) {
- apr_pool_create(&pool, apr_thread_pool_get(state->thd));
- thread_pool = pool;
+ if (state->tp) {
+ apr_allocator_t *ta = state->ta;
+ apr_memnode_t *node;
+
+ if (ta == NULL) {
+ ta = thread_alloc;
+ if (ta == NULL) {
+ if (apr_allocator_create(&ta) != APR_SUCCESS) {
+ apr_abortfunc_t abort_fn = apr_pool_abort_get(state->tp);
+ if (abort_fn)
+ abort_fn(APR_ENOMEM);
+ return NULL;
+ }
+ apr_allocator_max_free_set(ta, ap_max_mem_free);
+ apr_pool_cleanup_register(state->tp, ta, destroy_thread_alloc,
+ apr_pool_cleanup_null);
+ thread_alloc = ta;
}
- state->pool = pool;
+ state->ta = ta;
}
- return apr_palloc(pool, size);
+
+ node = apr_allocator_alloc(ta, SIZEOF_VOIDP_ALIGNED + size);
+ if (node == NULL) {
+ apr_abortfunc_t abort_fn = apr_pool_abort_get(state->tp);
+ if (abort_fn)
+ abort_fn(APR_ENOMEM);
+ return NULL;
+ }
+ *(void **)node->first_avail = node;
+ return node->first_avail + SIZEOF_VOIDP_ALIGNED;
}
#endif
@@ -354,8 +383,10 @@ static void private_free(void *block, void *ctx)
}
#if APREG_USE_THREAD_LOCAL
- if (state->thd) {
- /* Freed in cleanup_state() eventually. */
+ if (state->ta) {
+ /* This node allocated from thread allocator. Free/recycle it. */
+ apr_memnode_t *node = *(void **)(p - SIZEOF_VOIDP_ALIGNED);
+ apr_allocator_free(state->ta, node);
return;
}
#endif
@@ -369,8 +400,11 @@ int setup_state(struct match_data_state *state, ap
state->buf_used = 0;
#if APREG_USE_THREAD_LOCAL
- state->thd = ap_thread_current();
- state->pool = NULL;
+ {
+ apr_thread_t *thd = ap_thread_current();
+ state->tp = (thd) ? apr_thread_pool_get(thd) : NULL;
+ state->ta = NULL;
+ }
#endif
#ifdef HAVE_PCRE2
@@ -412,15 +446,6 @@ void cleanup_state(struct match_data_state *state)
private_free(state->match_data, state);
}
#endif
-
-#if APREG_USE_THREAD_LOCAL
- if (state->pool) {
- /* Let the thread's pool allocator recycle or free according
- * to its max_free setting.
- */
- apr_pool_clear(state->pool);
- }
-#endif
}
AP_DECLARE(int) ap_regexec(const ap_regex_t *preg, const char *string,
