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Fixed segfault when switching off master process during upgrade.

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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.
This commit is contained in:
Maxim Dounin 2022-11-23 23:48:53 +03:00
parent 0ef1d93199
commit 73c99585a5
2 changed files with 3 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
src/event/ngx_event.c
View file

@ -813,7 +813,9 @@ ngx_event_process_init(ngx_cycle_t *cycle)
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) {
/*

10
src/os/unix/ngx_process_cycle.c
View file

@ -759,7 +759,6 @@ ngx_worker_process_init(ngx_cycle_t *cycle, ngx_int_t worker)
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 *cycle, ngx_int_t worker)
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) {