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changeset 8106:8852f39311de

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Fixed segfault when switching off master process during upgrade. Binary upgrades are not supported without master process, but it is, however, possible, that nginx running with master process is asked to upgrade binary, and the configuration file as available on disk at this time includes "master_process off;". If this happens, listening sockets inherited from the previous binary will have ls[i].previous set. But the old cycle on initial process startup, including startup after binary upgrade, is destroyed by ngx_init_cycle() once configuration parsing is complete. As a result, an attempt to dereference ls[i].previous in ngx_event_process_init() accesses already freed memory. Fix is to avoid looking into ls[i].previous if the old cycle is already freed. With this change it is also no longer needed to clear ls[i].previous in worker processes, so the relevant code was removed.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 23 Nov 2022 23:48:53 +0300
parents 09463dd9c504
children 0b360747c74e
files src/event/ngx_event.c src/os/unix/ngx_process_cycle.c
diffstat 2 files changed, 3 insertions(+), 11 deletions(-) [+]
line wrap: on
line diff
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -813,7 +813,9 @@ ngx_event_process_init(ngx_cycle_t *cycl
         rev->deferred_accept = ls[i].deferred_accept;
 #endif
 
-        if (!(ngx_event_flags & NGX_USE_IOCP_EVENT)) {
+        if (!(ngx_event_flags & NGX_USE_IOCP_EVENT)
+            && cycle->old_cycle)
+        {
             if (ls[i].previous) {
 
                 /*
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -759,7 +759,6 @@ ngx_worker_process_init(ngx_cycle_t *cyc
     ngx_cpuset_t     *cpu_affinity;
     struct rlimit     rlmt;
     ngx_core_conf_t  *ccf;
-    ngx_listening_t  *ls;
 
     if (ngx_set_environment(cycle, NULL) == NULL) {
         /* fatal */
@@ -889,15 +888,6 @@ ngx_worker_process_init(ngx_cycle_t *cyc
     tp = ngx_timeofday();
     srandom(((unsigned) ngx_pid << 16) ^ tp->sec ^ tp->msec);
 
-    /*
-     * disable deleting previous events for the listening sockets because
-     * in the worker processes there are no events at all at this point
-     */
-    ls = cycle->listening.elts;
-    for (i = 0; i < cycle->listening.nelts; i++) {
-        ls[i].previous = NULL;
-    }
-
     for (i = 0; cycle->modules[i]; i++) {
         if (cycle->modules[i]->init_process) {
             if (cycle->modules[i]->init_process(cycle) == NGX_ERROR) {