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[nginx] Core: fixed environment on exit.

Maxim Dounin
December 07, 2016 12:50PM
details: http://hg.nginx.org/nginx/rev/c045b4926b2c
branches:
changeset: 6822:c045b4926b2c
user: Maxim Dounin <mdounin@mdounin.ru>
date: Wed Dec 07 19:03:31 2016 +0300
description:
Core: fixed environment on exit.

On exit environment allocated from a pool is no longer available, leading
to a segmentation fault if, for example, a library tries to use it from
an atexit() handler.

Fix is to allocate environment via ngx_alloc() instead, and explicitly
free it using a pool cleanup handler if it's no longer used (e.g., on
configuration reload).

diffstat:

src/core/nginx.c | 48 ++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 40 insertions(+), 8 deletions(-)

diffs (83 lines):

diff --git a/src/core/nginx.c b/src/core/nginx.c
--- a/src/core/nginx.c
+++ b/src/core/nginx.c
@@ -12,6 +12,7 @@

static void ngx_show_version_info(void);
static ngx_int_t ngx_add_inherited_sockets(ngx_cycle_t *cycle);
+static void ngx_cleanup_environment(void *data);
static ngx_int_t ngx_get_options(int argc, char *const *argv);
static ngx_int_t ngx_process_options(ngx_cycle_t *cycle);
static ngx_int_t ngx_save_argv(ngx_cycle_t *cycle, int argc, char *const *argv);
@@ -495,10 +496,11 @@ ngx_add_inherited_sockets(ngx_cycle_t *c
char **
ngx_set_environment(ngx_cycle_t *cycle, ngx_uint_t *last)
{
- char **p, **env;
- ngx_str_t *var;
- ngx_uint_t i, n;
- ngx_core_conf_t *ccf;
+ char **p, **env;
+ ngx_str_t *var;
+ ngx_uint_t i, n;
+ ngx_core_conf_t *ccf;
+ ngx_pool_cleanup_t *cln;

ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

@@ -550,14 +552,25 @@ tz_found:

if (last) {
env = ngx_alloc((*last + n + 1) * sizeof(char *), cycle->log);
+ if (env == NULL) {
+ return NULL;
+ }
+
*last = n;

} else {
- env = ngx_palloc(cycle->pool, (n + 1) * sizeof(char *));
- }
+ cln = ngx_pool_cleanup_add(cycle->pool, 0);
+ if (cln == NULL) {
+ return NULL;
+ }

- if (env == NULL) {
- return NULL;
+ env = ngx_alloc((n + 1) * sizeof(char *), cycle->log);
+ if (env == NULL) {
+ return NULL;
+ }
+
+ cln->handler = ngx_cleanup_environment;
+ cln->data = env;
}

n = 0;
@@ -591,6 +604,25 @@ tz_found:
}


+static void
+ngx_cleanup_environment(void *data)
+{
+ char **env = data;
+
+ if (environ == env) {
+
+ /*
+ * if the environment is still used, as it happens on exit,
+ * the only option is to leak it
+ */
+
+ return;
+ }
+
+ ngx_free(env);
+}
+
+
ngx_pid_t
ngx_exec_new_binary(ngx_cycle_t *cycle, char *const *argv)
{
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[nginx] Core: fixed environment on exit.

Maxim Dounin 266 December 07, 2016 12:50PM



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