view src/event/ngx_event_connectex.c @ 8106:8852f39311de

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 d620f497c50f
children 1c3b78d7cdc9
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


#define NGX_MAX_PENDING_CONN  10


static CRITICAL_SECTION  connect_lock;
static int               nconnects;
static ngx_connection_t  pending_connects[NGX_MAX_PENDING_CONN];

static HANDLE            pending_connect_event;

__declspec(thread) int                nevents = 0;
__declspec(thread) WSAEVENT           events[WSA_MAXIMUM_WAIT_EVENTS + 1];
__declspec(thread) ngx_connection_t  *conn[WSA_MAXIMUM_WAIT_EVENTS + 1];



int ngx_iocp_wait_connect(ngx_connection_t *c)
{
    for ( ;; ) {
        EnterCriticalSection(&connect_lock);

        if (nconnects < NGX_MAX_PENDING_CONN) {
            pending_connects[--nconnects] = c;
            LeaveCriticalSection(&connect_lock);

            if (SetEvent(pending_connect_event) == 0) {
                ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
                              "SetEvent() failed");
                return NGX_ERROR;

            break;
        }

        LeaveCriticalSection(&connect_lock);
        ngx_log_error(NGX_LOG_NOTICE, c->log, 0,
                      "max number of pending connect()s is %d",
                      NGX_MAX_PENDING_CONN);
        msleep(100);
    }

    if (!started) {
        if (ngx_iocp_new_thread(1) == NGX_ERROR) {
            return NGX_ERROR;
        }
        started = 1;
    }

    return NGX_OK;
}


int ngx_iocp_new_thread(int main)
{
    u_int  id;

    if (main) {
        pending_connect_event = CreateEvent(NULL, 0, 1, NULL);
        if (pending_connect_event == INVALID_HANDLE_VALUE) {
            ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
                          "CreateThread() failed");
            return NGX_ERROR;
        }
    }

    if (CreateThread(NULL, 0, ngx_iocp_wait_events, main, 0, &id)
                                                       == INVALID_HANDLE_VALUE)
    {
        ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
                      "CreateThread() failed");
        return NGX_ERROR;
    }

    SetEvent(event) {
        ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
                      "SetEvent() failed");
        return NGX_ERROR;
    }

    return NGX_OK;
}


int ngx_iocp_new_connect()
{
    EnterCriticalSection(&connect_lock);
    c = pending_connects[--nconnects];
    LeaveCriticalSection(&connect_lock);

    conn[nevents] = c;

    events[nevents] = WSACreateEvent();
    if (events[nevents] == INVALID_HANDLE_VALUE) {
        ngx_log_error(NGX_LOG_ALERT, c->log, ngx_socket_errno,
                      "WSACreateEvent() failed");
        return NGX_ERROR;
    }

    if (WSAEventSelect(c->fd, events[nevents], FD_CONNECT) == -1)
        ngx_log_error(NGX_LOG_ALERT, c->log, ngx_socket_errno,
                      "WSAEventSelect() failed");
        return NGX_ERROR;
    }

    nevents++;

    return NGX_OK;
}


void ngx_iocp_wait_events(int main)
{
    WSANETWORKEVENTS  ne;

    nevents = 1;
    events[0] = pending_connect_event;
    conn[0] = NULL;

    for ( ;; ) {
        offset = (nevents == WSA_MAXIMUM_WAIT_EVENTS + 1) ? 1: 0;
        timeout = (nevents == 1 && !first) ? 60000: INFINITE;

        n = WSAWaitForMultipleEvents(nevents - offset, events[offset],
                                     0, timeout, 0);
        if (n == WAIT_FAILED) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_socket_errno,
                          "WSAWaitForMultipleEvents() failed");
            continue;
        }

        if (n == WAIT_TIMEOUT) {
            if (nevents == 2 && !main) {
                ExitThread(0);
            }

            ngx_log_error(NGX_LOG_ALERT, log, 0,
                          "WSAWaitForMultipleEvents() "
                          "returned unexpected WAIT_TIMEOUT");
            continue;
        }

        n -= WSA_WAIT_EVENT_0;

        if (events[n] == NULL) {

            /* the pending_connect_event */

            if (nevents == WSA_MAXIMUM_WAIT_EVENTS) {
                ngx_iocp_new_thread(0);
            } else {
                ngx_iocp_new_connect();
            }

            continue;
        }

        if (WSAEnumNetworkEvents(c[n].fd, events[n], &ne) == -1) {
            ngx_log_error(NGX_LOG_ALERT, log, ngx_socket_errno,
                          "WSAEnumNetworkEvents() failed");
            continue;
        }

        if (ne.lNetworkEvents & FD_CONNECT) {
            conn[n].write->ovlp.error = ne.iErrorCode[FD_CONNECT_BIT];

            if (PostQueuedCompletionStatus(iocp, 0, NGX_IOCP_CONNECT,
                                           &conn[n].write->ovlp) == 0)
            {
                ngx_log_error(NGX_LOG_ALERT, log, ngx_socket_errno,
                              "PostQueuedCompletionStatus() failed");
                continue;
            }

            if (n < nevents) {
                conn[n] = conn[nevents];
                events[n] = events[nevents];
            }

            nevents--;
            continue;
        }

        if (ne.lNetworkEvents & FD_ACCEPT) {

            /* CHECK ERROR ??? */

            ngx_event_post_acceptex(conn[n].listening, 1);
            continue;
        }

        ngx_log_error(NGX_LOG_ALERT, c[n].log, 0,
                      "WSAWaitForMultipleEvents() "
                      "returned unexpected network event %ul",
                      ne.lNetworkEvents);
    }
}