Mercurial > hg > nginx
view src/core/ngx_log.c @ 6351:497d0cff8ace
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 | 2c21bfe3da89 |
children | 2cd019520210 |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> static char *ngx_error_log(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static char *ngx_log_set_levels(ngx_conf_t *cf, ngx_log_t *log); static void ngx_log_insert(ngx_log_t *log, ngx_log_t *new_log); #if (NGX_DEBUG) static void ngx_log_memory_writer(ngx_log_t *log, ngx_uint_t level, u_char *buf, size_t len); static void ngx_log_memory_cleanup(void *data); typedef struct { u_char *start; u_char *end; u_char *pos; ngx_atomic_t written; } ngx_log_memory_buf_t; #endif static ngx_command_t ngx_errlog_commands[] = { {ngx_string("error_log"), NGX_MAIN_CONF|NGX_CONF_1MORE, ngx_error_log, 0, 0, NULL}, ngx_null_command }; static ngx_core_module_t ngx_errlog_module_ctx = { ngx_string("errlog"), NULL, NULL }; ngx_module_t ngx_errlog_module = { NGX_MODULE_V1, &ngx_errlog_module_ctx, /* module context */ ngx_errlog_commands, /* module directives */ NGX_CORE_MODULE, /* module type */ NULL, /* init master */ NULL, /* init module */ NULL, /* init process */ NULL, /* init thread */ NULL, /* exit thread */ NULL, /* exit process */ NULL, /* exit master */ NGX_MODULE_V1_PADDING }; static ngx_log_t ngx_log; static ngx_open_file_t ngx_log_file; ngx_uint_t ngx_use_stderr = 1; static ngx_str_t err_levels[] = { ngx_null_string, ngx_string("emerg"), ngx_string("alert"), ngx_string("crit"), ngx_string("error"), ngx_string("warn"), ngx_string("notice"), ngx_string("info"), ngx_string("debug") }; static const char *debug_levels[] = { "debug_core", "debug_alloc", "debug_mutex", "debug_event", "debug_http", "debug_mail", "debug_mysql", "debug_stream" }; #if (NGX_HAVE_VARIADIC_MACROS) void ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err, const char *fmt, ...) #else void ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err, const char *fmt, va_list args) #endif { #if (NGX_HAVE_VARIADIC_MACROS) va_list args; #endif u_char *p, *last, *msg; ssize_t n; ngx_uint_t wrote_stderr, debug_connection; u_char errstr[NGX_MAX_ERROR_STR]; last = errstr + NGX_MAX_ERROR_STR; p = ngx_cpymem(errstr, ngx_cached_err_log_time.data, ngx_cached_err_log_time.len); p = ngx_slprintf(p, last, " [%V] ", &err_levels[level]); /* pid#tid */ p = ngx_slprintf(p, last, "%P#" NGX_TID_T_FMT ": ", ngx_log_pid, ngx_log_tid); if (log->connection) { p = ngx_slprintf(p, last, "*%uA ", log->connection); } msg = p; #if (NGX_HAVE_VARIADIC_MACROS) va_start(args, fmt); p = ngx_vslprintf(p, last, fmt, args); va_end(args); #else p = ngx_vslprintf(p, last, fmt, args); #endif if (err) { p = ngx_log_errno(p, last, err); } if (level != NGX_LOG_DEBUG && log->handler) { p = log->handler(log, p, last - p); } if (p > last - NGX_LINEFEED_SIZE) { p = last - NGX_LINEFEED_SIZE; } ngx_linefeed(p); wrote_stderr = 0; debug_connection = (log->log_level & NGX_LOG_DEBUG_CONNECTION) != 0; while (log) { if (log->log_level < level && !debug_connection) { break; } if (log->writer) { log->writer(log, level, errstr, p - errstr); goto next; } if (ngx_time() == log->disk_full_time) { /* * on FreeBSD writing to a full filesystem with enabled softupdates * may block process for much longer time than writing to non-full * filesystem, so we skip writing to a log for one second */ goto next; } n = ngx_write_fd(log->file->fd, errstr, p - errstr); if (n == -1 && ngx_errno == NGX_ENOSPC) { log->disk_full_time = ngx_time(); } if (log->file->fd == ngx_stderr) { wrote_stderr = 1; } next: log = log->next; } if (!ngx_use_stderr || level > NGX_LOG_WARN || wrote_stderr) { return; } msg -= (7 + err_levels[level].len + 3); (void) ngx_sprintf(msg, "nginx: [%V] ", &err_levels[level]); (void) ngx_write_console(ngx_stderr, msg, p - msg); } #if !(NGX_HAVE_VARIADIC_MACROS) void ngx_cdecl ngx_log_error(ngx_uint_t level, ngx_log_t *log, ngx_err_t err, const char *fmt, ...) { va_list args; if (log->log_level >= level) { va_start(args, fmt); ngx_log_error_core(level, log, err, fmt, args); va_end(args); } } void ngx_cdecl ngx_log_debug_core(ngx_log_t *log, ngx_err_t err, const char *fmt, ...) { va_list args; va_start(args, fmt); ngx_log_error_core(NGX_LOG_DEBUG, log, err, fmt, args); va_end(args); } #endif void ngx_cdecl ngx_log_abort(ngx_err_t err, const char *fmt, ...) { u_char *p; va_list args; u_char errstr[NGX_MAX_CONF_ERRSTR]; va_start(args, fmt); p = ngx_vsnprintf(errstr, sizeof(errstr) - 1, fmt, args); va_end(args); ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, err, "%*s", p - errstr, errstr); } void ngx_cdecl ngx_log_stderr(ngx_err_t err, const char *fmt, ...) { u_char *p, *last; va_list args; u_char errstr[NGX_MAX_ERROR_STR]; last = errstr + NGX_MAX_ERROR_STR; p = ngx_cpymem(errstr, "nginx: ", 7); va_start(args, fmt); p = ngx_vslprintf(p, last, fmt, args); va_end(args); if (err) { p = ngx_log_errno(p, last, err); } if (p > last - NGX_LINEFEED_SIZE) { p = last - NGX_LINEFEED_SIZE; } ngx_linefeed(p); (void) ngx_write_console(ngx_stderr, errstr, p - errstr); } u_char * ngx_log_errno(u_char *buf, u_char *last, ngx_err_t err) { if (buf > last - 50) { /* leave a space for an error code */ buf = last - 50; *buf++ = '.'; *buf++ = '.'; *buf++ = '.'; } #if (NGX_WIN32) buf = ngx_slprintf(buf, last, ((unsigned) err < 0x80000000) ? " (%d: " : " (%Xd: ", err); #else buf = ngx_slprintf(buf, last, " (%d: ", err); #endif buf = ngx_strerror(err, buf, last - buf); if (buf < last) { *buf++ = ')'; } return buf; } ngx_log_t * ngx_log_init(u_char *prefix) { u_char *p, *name; size_t nlen, plen; ngx_log.file = &ngx_log_file; ngx_log.log_level = NGX_LOG_NOTICE; name = (u_char *) NGX_ERROR_LOG_PATH; /* * we use ngx_strlen() here since BCC warns about * condition is always false and unreachable code */ nlen = ngx_strlen(name); if (nlen == 0) { ngx_log_file.fd = ngx_stderr; return &ngx_log; } p = NULL; #if (NGX_WIN32) if (name[1] != ':') { #else if (name[0] != '/') { #endif if (prefix) { plen = ngx_strlen(prefix); } else { #ifdef NGX_PREFIX prefix = (u_char *) NGX_PREFIX; plen = ngx_strlen(prefix); #else plen = 0; #endif } if (plen) { name = malloc(plen + nlen + 2); if (name == NULL) { return NULL; } p = ngx_cpymem(name, prefix, plen); if (!ngx_path_separator(*(p - 1))) { *p++ = '/'; } ngx_cpystrn(p, (u_char *) NGX_ERROR_LOG_PATH, nlen + 1); p = name; } } ngx_log_file.fd = ngx_open_file(name, NGX_FILE_APPEND, NGX_FILE_CREATE_OR_OPEN, NGX_FILE_DEFAULT_ACCESS); if (ngx_log_file.fd == NGX_INVALID_FILE) { ngx_log_stderr(ngx_errno, "[alert] could not open error log file: " ngx_open_file_n " \"%s\" failed", name); #if (NGX_WIN32) ngx_event_log(ngx_errno, "could not open error log file: " ngx_open_file_n " \"%s\" failed", name); #endif ngx_log_file.fd = ngx_stderr; } if (p) { ngx_free(p); } return &ngx_log; } ngx_int_t ngx_log_open_default(ngx_cycle_t *cycle) { ngx_log_t *log; static ngx_str_t error_log = ngx_string(NGX_ERROR_LOG_PATH); if (ngx_log_get_file_log(&cycle->new_log) != NULL) { return NGX_OK; } if (cycle->new_log.log_level != 0) { /* there are some error logs, but no files */ log = ngx_pcalloc(cycle->pool, sizeof(ngx_log_t)); if (log == NULL) { return NGX_ERROR; } } else { /* no error logs at all */ log = &cycle->new_log; } log->log_level = NGX_LOG_ERR; log->file = ngx_conf_open_file(cycle, &error_log); if (log->file == NULL) { return NGX_ERROR; } if (log != &cycle->new_log) { ngx_log_insert(&cycle->new_log, log); } return NGX_OK; } ngx_int_t ngx_log_redirect_stderr(ngx_cycle_t *cycle) { ngx_fd_t fd; if (cycle->log_use_stderr) { return NGX_OK; } /* file log always exists when we are called */ fd = ngx_log_get_file_log(cycle->log)->file->fd; if (fd != ngx_stderr) { if (ngx_set_stderr(fd) == NGX_FILE_ERROR) { ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno, ngx_set_stderr_n " failed"); return NGX_ERROR; } } return NGX_OK; } ngx_log_t * ngx_log_get_file_log(ngx_log_t *head) { ngx_log_t *log; for (log = head; log; log = log->next) { if (log->file != NULL) { return log; } } return NULL; } static char * ngx_log_set_levels(ngx_conf_t *cf, ngx_log_t *log) { ngx_uint_t i, n, d, found; ngx_str_t *value; if (cf->args->nelts == 2) { log->log_level = NGX_LOG_ERR; return NGX_CONF_OK; } value = cf->args->elts; for (i = 2; i < cf->args->nelts; i++) { found = 0; for (n = 1; n <= NGX_LOG_DEBUG; n++) { if (ngx_strcmp(value[i].data, err_levels[n].data) == 0) { if (log->log_level != 0) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "duplicate log level \"%V\"", &value[i]); return NGX_CONF_ERROR; } log->log_level = n; found = 1; break; } } for (n = 0, d = NGX_LOG_DEBUG_FIRST; d <= NGX_LOG_DEBUG_LAST; d <<= 1) { if (ngx_strcmp(value[i].data, debug_levels[n++]) == 0) { if (log->log_level & ~NGX_LOG_DEBUG_ALL) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid log level \"%V\"", &value[i]); return NGX_CONF_ERROR; } log->log_level |= d; found = 1; break; } } if (!found) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid log level \"%V\"", &value[i]); return NGX_CONF_ERROR; } } if (log->log_level == NGX_LOG_DEBUG) { log->log_level = NGX_LOG_DEBUG_ALL; } return NGX_CONF_OK; } static char * ngx_error_log(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_log_t *dummy; dummy = &cf->cycle->new_log; return ngx_log_set_log(cf, &dummy); } char * ngx_log_set_log(ngx_conf_t *cf, ngx_log_t **head) { ngx_log_t *new_log; ngx_str_t *value, name; ngx_syslog_peer_t *peer; if (*head != NULL && (*head)->log_level == 0) { new_log = *head; } else { new_log = ngx_pcalloc(cf->pool, sizeof(ngx_log_t)); if (new_log == NULL) { return NGX_CONF_ERROR; } if (*head == NULL) { *head = new_log; } } value = cf->args->elts; if (ngx_strcmp(value[1].data, "stderr") == 0) { ngx_str_null(&name); cf->cycle->log_use_stderr = 1; new_log->file = ngx_conf_open_file(cf->cycle, &name); if (new_log->file == NULL) { return NGX_CONF_ERROR; } } else if (ngx_strncmp(value[1].data, "memory:", 7) == 0) { #if (NGX_DEBUG) size_t size, needed; ngx_pool_cleanup_t *cln; ngx_log_memory_buf_t *buf; value[1].len -= 7; value[1].data += 7; needed = sizeof("MEMLOG :" NGX_LINEFEED) + cf->conf_file->file.name.len + NGX_SIZE_T_LEN + NGX_INT_T_LEN + NGX_MAX_ERROR_STR; size = ngx_parse_size(&value[1]); if (size == (size_t) NGX_ERROR || size < needed) { ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid buffer size \"%V\"", &value[1]); return NGX_CONF_ERROR; } buf = ngx_pcalloc(cf->pool, sizeof(ngx_log_memory_buf_t)); if (buf == NULL) { return NGX_CONF_ERROR; } buf->start = ngx_pnalloc(cf->pool, size); if (buf->start == NULL) { return NGX_CONF_ERROR; } buf->end = buf->start + size; buf->pos = ngx_slprintf(buf->start, buf->end, "MEMLOG %uz %V:%ui%N", size, &cf->conf_file->file.name, cf->conf_file->line); ngx_memset(buf->pos, ' ', buf->end - buf->pos); cln = ngx_pool_cleanup_add(cf->pool, 0); if (cln == NULL) { return NGX_CONF_ERROR; } cln->data = new_log; cln->handler = ngx_log_memory_cleanup; new_log->writer = ngx_log_memory_writer; new_log->wdata = buf; #else ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "nginx was built without debug support"); return NGX_CONF_ERROR; #endif } else if (ngx_strncmp(value[1].data, "syslog:", 7) == 0) { peer = ngx_pcalloc(cf->pool, sizeof(ngx_syslog_peer_t)); if (peer == NULL) { return NGX_CONF_ERROR; } if (ngx_syslog_process_conf(cf, peer) != NGX_CONF_OK) { return NGX_CONF_ERROR; } new_log->writer = ngx_syslog_writer; new_log->wdata = peer; } else { new_log->file = ngx_conf_open_file(cf->cycle, &value[1]); if (new_log->file == NULL) { return NGX_CONF_ERROR; } } if (ngx_log_set_levels(cf, new_log) != NGX_CONF_OK) { return NGX_CONF_ERROR; } if (*head != new_log) { ngx_log_insert(*head, new_log); } return NGX_CONF_OK; } static void ngx_log_insert(ngx_log_t *log, ngx_log_t *new_log) { ngx_log_t tmp; if (new_log->log_level > log->log_level) { /* * list head address is permanent, insert new log after * head and swap its contents with head */ tmp = *log; *log = *new_log; *new_log = tmp; log->next = new_log; return; } while (log->next) { if (new_log->log_level > log->next->log_level) { new_log->next = log->next; log->next = new_log; return; } log = log->next; } log->next = new_log; } #if (NGX_DEBUG) static void ngx_log_memory_writer(ngx_log_t *log, ngx_uint_t level, u_char *buf, size_t len) { u_char *p; size_t avail, written; ngx_log_memory_buf_t *mem; mem = log->wdata; if (mem == NULL) { return; } written = ngx_atomic_fetch_add(&mem->written, len); p = mem->pos + written % (mem->end - mem->pos); avail = mem->end - p; if (avail >= len) { ngx_memcpy(p, buf, len); } else { ngx_memcpy(p, buf, avail); ngx_memcpy(mem->pos, buf + avail, len - avail); } } static void ngx_log_memory_cleanup(void *data) { ngx_log_t *log = data; ngx_log_debug0(NGX_LOG_DEBUG_CORE, log, 0, "destroy memory log buffer"); log->wdata = NULL; } #endif