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[nginx] Core: fixed ngx_pcre_studies cleanup.

Maxim Dounin
December 24, 2021 05:12PM
details: https://hg.nginx.org/nginx/rev/2ca57257252d
branches:
changeset: 7978:2ca57257252d
user: Maxim Dounin <mdounin@mdounin.ru>
date: Sat Dec 25 01:07:10 2021 +0300
description:
Core: fixed ngx_pcre_studies cleanup.

If a configuration parsing fails for some reason, ngx_regex_module_init()
is not called, and ngx_pcre_studies remained set despite the fact that
the pool it was allocated from is already freed. This might result in
a segmentation fault during runtime regular expression compilation, such
as in SSI, for example, in the single process mode, or if a worker process
died and was respawned from a master process in such an inconsistent state.

Fix is to clear ngx_pcre_studies from the pool cleanup handler (which is
anyway used to free JIT-compiled patterns).

diffstat:

src/core/ngx_regex.c | 103 ++++++++++++++++++++++++++------------------------
1 files changed, 53 insertions(+), 50 deletions(-)

diffs (168 lines):

diff -r 336084ff943b -r 2ca57257252d src/core/ngx_regex.c
--- a/src/core/ngx_regex.c Tue Dec 21 07:54:16 2021 +0300
+++ b/src/core/ngx_regex.c Sat Dec 25 01:07:10 2021 +0300
@@ -10,15 +10,14 @@


typedef struct {
- ngx_flag_t pcre_jit;
+ ngx_flag_t pcre_jit;
+ ngx_list_t *studies;
} ngx_regex_conf_t;


static void * ngx_libc_cdecl ngx_regex_malloc(size_t size);
static void ngx_libc_cdecl ngx_regex_free(void *p);
-#if (NGX_HAVE_PCRE_JIT)
-static void ngx_pcre_free_studies(void *data);
-#endif
+static void ngx_regex_cleanup(void *data);

static ngx_int_t ngx_regex_module_init(ngx_cycle_t *cycle);

@@ -248,18 +247,17 @@ ngx_regex_free(void *p)
}


+static void
+ngx_regex_cleanup(void *data)
+{
#if (NGX_HAVE_PCRE_JIT)
-
-static void
-ngx_pcre_free_studies(void *data)
-{
- ngx_list_t *studies = data;
+ ngx_regex_conf_t *rcf = data;

ngx_uint_t i;
ngx_list_part_t *part;
ngx_regex_elt_t *elts;

- part = &studies->part;
+ part = &rcf->studies->part;
elts = part->elts;

for (i = 0; /* void */ ; i++) {
@@ -274,56 +272,50 @@ ngx_pcre_free_studies(void *data)
i = 0;
}

- if (elts[i].regex->extra != NULL) {
- pcre_free_study(elts[i].regex->extra);
- }
- }
-}
-
-#endif
-
-
-static ngx_int_t
-ngx_regex_module_init(ngx_cycle_t *cycle)
-{
- int opt;
- const char *errstr;
- ngx_uint_t i;
- ngx_list_part_t *part;
- ngx_regex_elt_t *elts;
-
- opt = 0;
-
-#if (NGX_HAVE_PCRE_JIT)
- {
- ngx_regex_conf_t *rcf;
- ngx_pool_cleanup_t *cln;
-
- rcf = (ngx_regex_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_regex_module);
-
- if (rcf->pcre_jit) {
- opt = PCRE_STUDY_JIT_COMPILE;
-
/*
* The PCRE JIT compiler uses mmap for its executable codes, so we
* have to explicitly call the pcre_free_study() function to free
* this memory.
*/

- cln = ngx_pool_cleanup_add(cycle->pool, 0);
- if (cln == NULL) {
- return NGX_ERROR;
+ if (elts[i].regex->extra != NULL) {
+ pcre_free_study(elts[i].regex->extra);
}
+ }
+#endif

- cln->handler = ngx_pcre_free_studies;
- cln->data = ngx_pcre_studies;
- }
+ /*
+ * On configuration parsing errors ngx_regex_module_init() will not
+ * be called. Make sure ngx_pcre_studies is properly cleared anyway.
+ */
+
+ ngx_pcre_studies = NULL;
+}
+
+
+static ngx_int_t
+ngx_regex_module_init(ngx_cycle_t *cycle)
+{
+ int opt;
+ const char *errstr;
+ ngx_uint_t i;
+ ngx_list_part_t *part;
+ ngx_regex_elt_t *elts;
+ ngx_regex_conf_t *rcf;
+
+ opt = 0;
+
+ rcf = (ngx_regex_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_regex_module);
+
+#if (NGX_HAVE_PCRE_JIT)
+ if (rcf->pcre_jit) {
+ opt = PCRE_STUDY_JIT_COMPILE;
}
#endif

ngx_regex_malloc_init(cycle->pool);

- part = &ngx_pcre_studies->part;
+ part = &rcf->studies->part;
elts = part->elts;

for (i = 0; /* void */ ; i++) {
@@ -374,7 +366,8 @@ ngx_regex_module_init(ngx_cycle_t *cycle
static void *
ngx_regex_create_conf(ngx_cycle_t *cycle)
{
- ngx_regex_conf_t *rcf;
+ ngx_regex_conf_t *rcf;
+ ngx_pool_cleanup_t *cln;

rcf = ngx_pcalloc(cycle->pool, sizeof(ngx_regex_conf_t));
if (rcf == NULL) {
@@ -383,11 +376,21 @@ ngx_regex_create_conf(ngx_cycle_t *cycle

rcf->pcre_jit = NGX_CONF_UNSET;

- ngx_pcre_studies = ngx_list_create(cycle->pool, 8, sizeof(ngx_regex_elt_t));
- if (ngx_pcre_studies == NULL) {
+ cln = ngx_pool_cleanup_add(cycle->pool, 0);
+ if (cln == NULL) {
return NULL;
}

+ cln->handler = ngx_regex_cleanup;
+ cln->data = rcf;
+
+ rcf->studies = ngx_list_create(cycle->pool, 8, sizeof(ngx_regex_elt_t));
+ if (rcf->studies == NULL) {
+ return NULL;
+ }
+
+ ngx_pcre_studies = rcf->studies;
+
return rcf;
}

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[nginx] Core: fixed ngx_pcre_studies cleanup.

Maxim Dounin 273 December 24, 2021 05:12PM



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