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Resolver: fixed use-after-free memory accesses with CNAME. When several requests were waiting for a response, then after getting a CNAME response only the last request's context had the name updated. Contexts of other requests had the wrong name. This name was used by ngx_resolve_name_done() to find the node to remove the request context from. When the name was wrong, the request could not be properly cancelled, its context was freed but stayed linked to the node's waiting list. This happened e.g. when the first request was aborted or timed out before the resolving completed. When it completed, this triggered a use-after-free memory access by calling ctx->handler of already freed request context. The bug manifests itself by "could not cancel <name> resolving" alerts in error_log. When a request was responded with a CNAME, the request context kept the pointer to the original node's rn->u.cname. If the original node expired before the resolving timed out or completed with an error, this would trigger a use-after-free memory access via ctx->name in ctx->handler(). The fix is to keep ctx->name unmodified. The name from context is no longer used by ngx_resolve_name_done(). Instead, we now keep the pointer to resolver node to which this request is linked. Keeping the original name intact also improves logging.
author Roman Arutyunyan <arut@nginx.com>
date Tue, 26 Jan 2016 16:46:59 +0300
parents 96c4297375bc
children cf5e822cf470
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_CYCLE_H_INCLUDED_
#define _NGX_CYCLE_H_INCLUDED_


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


#ifndef NGX_CYCLE_POOL_SIZE
#define NGX_CYCLE_POOL_SIZE     NGX_DEFAULT_POOL_SIZE
#endif


#define NGX_DEBUG_POINTS_STOP   1
#define NGX_DEBUG_POINTS_ABORT  2


typedef struct ngx_shm_zone_s  ngx_shm_zone_t;

typedef ngx_int_t (*ngx_shm_zone_init_pt) (ngx_shm_zone_t *zone, void *data);

struct ngx_shm_zone_s {
    void                     *data;
    ngx_shm_t                 shm;
    ngx_shm_zone_init_pt      init;
    void                     *tag;
    ngx_uint_t                noreuse;  /* unsigned  noreuse:1; */
};


struct ngx_cycle_s {
    void                  ****conf_ctx;
    ngx_pool_t               *pool;

    ngx_log_t                *log;
    ngx_log_t                 new_log;

    ngx_uint_t                log_use_stderr;  /* unsigned  log_use_stderr:1; */

    ngx_connection_t        **files;
    ngx_connection_t         *free_connections;
    ngx_uint_t                free_connection_n;

    ngx_queue_t               reusable_connections_queue;

    ngx_array_t               listening;
    ngx_array_t               paths;
    ngx_array_t               config_dump;
    ngx_list_t                open_files;
    ngx_list_t                shared_memory;

    ngx_uint_t                connection_n;
    ngx_uint_t                files_n;

    ngx_connection_t         *connections;
    ngx_event_t              *read_events;
    ngx_event_t              *write_events;

    ngx_cycle_t              *old_cycle;

    ngx_str_t                 conf_file;
    ngx_str_t                 conf_param;
    ngx_str_t                 conf_prefix;
    ngx_str_t                 prefix;
    ngx_str_t                 lock_file;
    ngx_str_t                 hostname;
};


typedef struct {
     ngx_flag_t               daemon;
     ngx_flag_t               master;

     ngx_msec_t               timer_resolution;

     ngx_int_t                worker_processes;
     ngx_int_t                debug_points;

     ngx_int_t                rlimit_nofile;
     off_t                    rlimit_core;

     int                      priority;

     ngx_uint_t               cpu_affinity_auto;
     ngx_uint_t               cpu_affinity_n;
     uint64_t                *cpu_affinity;

     char                    *username;
     ngx_uid_t                user;
     ngx_gid_t                group;

     ngx_str_t                working_directory;
     ngx_str_t                lock_file;

     ngx_str_t                pid;
     ngx_str_t                oldpid;

     ngx_array_t              env;
     char                   **environment;
} ngx_core_conf_t;


#define ngx_is_init_cycle(cycle)  (cycle->conf_ctx == NULL)


ngx_cycle_t *ngx_init_cycle(ngx_cycle_t *old_cycle);
ngx_int_t ngx_create_pidfile(ngx_str_t *name, ngx_log_t *log);
void ngx_delete_pidfile(ngx_cycle_t *cycle);
ngx_int_t ngx_signal_process(ngx_cycle_t *cycle, char *sig);
void ngx_reopen_files(ngx_cycle_t *cycle, ngx_uid_t user);
char **ngx_set_environment(ngx_cycle_t *cycle, ngx_uint_t *last);
ngx_pid_t ngx_exec_new_binary(ngx_cycle_t *cycle, char *const *argv);
uint64_t ngx_get_cpu_affinity(ngx_uint_t n);
ngx_shm_zone_t *ngx_shared_memory_add(ngx_conf_t *cf, ngx_str_t *name,
    size_t size, void *tag);


extern volatile ngx_cycle_t  *ngx_cycle;
extern ngx_array_t            ngx_old_cycles;
extern ngx_module_t           ngx_core_module;
extern ngx_uint_t             ngx_test_config;
extern ngx_uint_t             ngx_dump_config;
extern ngx_uint_t             ngx_quiet_mode;


#endif /* _NGX_CYCLE_H_INCLUDED_ */