[OE-core] [PATCH v2] lighttpd: Fix mod_cgi to avoid it buffers data without bound.
Jussi Kukkonen
jussi.kukkonen at intel.com
Mon Jul 13 07:32:34 UTC 2015
On 13 July 2015 at 08:34, Li xin <lixin.fnst at cn.fujitsu.com> wrote:
> If there is a CGI that provides a continuous stream of data,
> if lighttpd client reads slower then the CGI is pushing the data,
> then lighttpd's buffers will grow until the (embedded) machine OOMs.
>
> Ref: http://redmine.lighttpd.net/issues/1264
>
> Signed-off-by: Li Xin <lixin.fnst at cn.fujitsu.com>
> ---
> .../0001-mod_cgi-buffers-data-without-bound.patch | 389 +++++++++++++++++++++
> meta/recipes-extended/lighttpd/lighttpd_1.4.35.bb | 1 +
> 2 files changed, 390 insertions(+)
> create mode 100644 meta/recipes-extended/lighttpd/lighttpd/0001-mod_cgi-buffers-data-without-bound.patch
>
> diff --git a/meta/recipes-extended/lighttpd/lighttpd/0001-mod_cgi-buffers-data-without-bound.patch b/meta/recipes-extended/lighttpd/lighttpd/0001-mod_cgi-buffers-data-without-bound.patch
> new file mode 100644
> index 0000000..c04f078
> --- /dev/null
> +++ b/meta/recipes-extended/lighttpd/lighttpd/0001-mod_cgi-buffers-data-without-bound.patch
> @@ -0,0 +1,389 @@
> +From e6ccbab5d42b110ac4f6ce1f72cb1e9ccbe4400a Mon Sep 17 00:00:00 2001
> +From: Li xin <lixin.fnst at cn.fujitsu.com>
> +Date: Tue, 16 Jun 2015 19:02:38 +0900
> +Subject: [PATCH] mod_cgi buffers data without bound so fix it
> +
> +Upstream-Status: Backport
> +it will be fixed in version 1.5.0
Is this really in an upstream branch somewhere? It's not clear from
the bug that it is (last updated 8 years ago, no comments from
lighttpd developers). If the patch is just taken from the bug report
then a "Upstream-Status: Submitted
[http://redmine.lighttpd.net/issues/1264]" would be more factual.
> +
> +Ref: http://redmine.lighttpd.net/issues/1264
> +
> +Signed-off-by: Li Xin <lixin.fnst at cn.fujitsu.com>
> +---
> + doc/config/lighttpd.conf | 8 ++
> + src/mod_cgi.c | 188 ++++++++++++++++++++++++++++++++++++++++++++---
> + 2 files changed, 186 insertions(+), 10 deletions(-)
> +
> +diff --git a/doc/config/lighttpd.conf b/doc/config/lighttpd.conf
> +index 60b0ae1..9c101a7 100644
> +--- a/doc/config/lighttpd.conf
> ++++ b/doc/config/lighttpd.conf
> +@@ -375,6 +375,14 @@ server.upload-dirs = ( "/var/tmp" )
> + ##
> + #######################################################################
> +
> ++#######################################################################
> ++##
> ++##
> ++## maximum bytes in send_raw before backing off [KByte]
> ++## cgi.high-waterlevel = 10240
> ++## minimum bytes in send_raw to disable backoff [KByte]
> ++## cgi.low-waterlevel = 5120
> ++#######################################################################
> +
> + #######################################################################
> + ##
> +diff --git a/src/mod_cgi.c b/src/mod_cgi.c
> +index 734ecee..c51f43c 100644
> +--- a/src/mod_cgi.c
> ++++ b/src/mod_cgi.c
> +@@ -38,6 +38,10 @@
> +
> + #include "version.h"
> +
> ++/* for output logs */
> ++char msgbuf[2048];
> ++
> ++
> + enum {EOL_UNSET, EOL_N, EOL_RN};
> +
> + typedef struct {
> +@@ -53,9 +57,19 @@ typedef struct {
> + size_t size;
> + } buffer_pid_t;
> +
> ++struct handler_ctx;
> ++
> ++typedef struct {
> ++ struct handler_ctx **hctx;
> ++ size_t used;
> ++ size_t size;
> ++} buffer_ctx_t;
> ++
> + typedef struct {
> + array *cgi;
> + unsigned short execute_x_only;
> ++ unsigned int high_waterlevel; /* maximum bytes in send_raw before backing off */
> ++ unsigned int low_waterlevel; /* minimum bytes in send_raw to disable backoff */
> + } plugin_config;
> +
> + typedef struct {
> +@@ -68,9 +82,11 @@ typedef struct {
> + plugin_config **config_storage;
> +
> + plugin_config conf;
> ++
> ++ buffer_ctx_t cgi_ctx;
> + } plugin_data;
> +
> +-typedef struct {
> ++typedef struct handler_ctx {
> + pid_t pid;
> + int fd;
> + int fde_ndx; /* index into the fd-event buffer */
> +@@ -78,11 +94,16 @@ typedef struct {
> + connection *remote_conn; /* dumb pointer */
> + plugin_data *plugin_data; /* dumb pointer */
> +
> ++ int throttling; /* 1=waiting for send_raw buffer to drain */
> ++ off_t high_waterlevel; /* maximum bytes in send_raw before backing off */
> ++ off_t low_waterlevel; /* minimum bytes in send_raw to disable backoff */
> ++ off_t bytes_in_buffer;
> ++
> + buffer *response;
> + buffer *response_header;
> + } handler_ctx;
> +
> +-static handler_ctx * cgi_handler_ctx_init(void) {
> ++static handler_ctx * cgi_handler_ctx_init(plugin_data *p) {
> + handler_ctx *hctx = calloc(1, sizeof(*hctx));
> +
> + force_assert(hctx);
> +@@ -90,13 +111,26 @@ static handler_ctx * cgi_handler_ctx_init(void) {
> + hctx->response = buffer_init();
> + hctx->response_header = buffer_init();
> +
> ++ hctx->throttling = 0;
> ++ hctx->high_waterlevel = (off_t)p->conf.high_waterlevel * 1024;
> ++ hctx->low_waterlevel = (off_t)p->conf.low_waterlevel * 1024;
> ++ if (hctx->low_waterlevel >= hctx->high_waterlevel) {
> ++ hctx->low_waterlevel = hctx->high_waterlevel * 3 / 4; /* 75% */
> ++ }
> ++ hctx->bytes_in_buffer = 0;
> ++
> + return hctx;
> + }
> +
> +-static void cgi_handler_ctx_free(handler_ctx *hctx) {
> ++static void cgi_handler_ctx_free(server *srv, handler_ctx *hctx) {
> + buffer_free(hctx->response);
> + buffer_free(hctx->response_header);
> +
> ++ /* to avoid confusion */
> ++ if (hctx->throttling) {
> ++ log_error_write(srv, __FILE__, __LINE__, "s", "unthrottled");
> ++ }
> ++
> + free(hctx);
> + }
> +
> +@@ -152,6 +186,8 @@ SETDEFAULTS_FUNC(mod_fastcgi_set_defaults) {
> + config_values_t cv[] = {
> + { "cgi.assign", NULL, T_CONFIG_ARRAY, T_CONFIG_SCOPE_CONNECTION }, /* 0 */
> + { "cgi.execute-x-only", NULL, T_CONFIG_BOOLEAN, T_CONFIG_SCOPE_CONNECTION }, /* 1 */
> ++ { "cgi.high-waterlevel", NULL, T_CONFIG_INT, T_CONFIG_SCOPE_CONNECTION }, /* 2 */
> ++ { "cgi.low-waterlevel", NULL, T_CONFIG_INT, T_CONFIG_SCOPE_CONNECTION }, /* 3 */
> + { NULL, NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET}
> + };
> +
> +@@ -167,9 +203,13 @@ SETDEFAULTS_FUNC(mod_fastcgi_set_defaults) {
> +
> + s->cgi = array_init();
> + s->execute_x_only = 0;
> ++ s->high_waterlevel = 0; /* 0 == disabled */
> ++ s->low_waterlevel = 0;
> +
> + cv[0].destination = s->cgi;
> + cv[1].destination = &(s->execute_x_only);
> ++ cv[2].destination = &(s->high_waterlevel);
> ++ cv[3].destination = &(s->low_waterlevel);
> +
> + p->config_storage[i] = s;
> +
> +@@ -182,6 +222,51 @@ SETDEFAULTS_FUNC(mod_fastcgi_set_defaults) {
> + }
> +
> +
> ++static void cgi_recount_bytes_in_buffer(handler_ctx *hctx)
> ++{
> ++ chunkqueue *cq = hctx->remote_conn->write_queue;
> ++ hctx->bytes_in_buffer = chunkqueue_length(cq) - chunkqueue_written(cq);
> ++}
> ++
> ++
> ++static void cgi_throttling_control(server *srv, handler_ctx *hctx)
> ++{
> ++ cgi_recount_bytes_in_buffer(hctx);
> ++
> ++#ifdef DEBUG
> ++ sprintf(msgbuf, "throttling=%d, chars=%llu, high=%llu, low=%llu",
> ++ hctx->throttling, hctx->bytes_in_buffer,
> ++ hctx->high_waterlevel, hctx->low_waterlevel);
> ++ log_error_write(srv, __FILE__, __LINE__, "ss",
> ++ "(debug) throttling control,", msgbuf);
> ++#endif
> ++
> ++ if (hctx->throttling) {
> ++ sprintf(msgbuf, "throttling; chars in queue=%llu,"
> ++ " low-waterlevel=%llu, high-waterlevel=%llu",
> ++ hctx->bytes_in_buffer,
> ++ hctx->low_waterlevel, hctx->high_waterlevel);
> ++ log_error_write(srv, __FILE__, __LINE__, "s", msgbuf);
> ++ if (hctx->bytes_in_buffer <= hctx->low_waterlevel) {
> ++ fdevent_event_set(srv->ev, &(hctx->fde_ndx), hctx->fd, FDEVENT_IN);
> ++ hctx->throttling = 0;
> ++ log_error_write(srv, __FILE__, __LINE__, "s", "unthrottled");
> ++ }
> ++ } else {
> ++ if (hctx->high_waterlevel != 0 &&
> ++ hctx->high_waterlevel <= hctx->bytes_in_buffer) {
> ++ fdevent_event_del(srv->ev, &(hctx->fde_ndx), hctx->fd);
> ++ hctx->throttling = 1;
> ++ sprintf(msgbuf, "throttled; chars in queue=%llu,"
> ++ " low-waterlevel=%llu, high-waterlevel=%llu",
> ++ hctx->bytes_in_buffer,
> ++ hctx->low_waterlevel, hctx->high_waterlevel);
> ++ log_error_write(srv, __FILE__, __LINE__, "s", msgbuf);
> ++ }
> ++ }
> ++}
> ++
> ++
> + static int cgi_pid_add(server *srv, plugin_data *p, pid_t pid) {
> + int m = -1;
> + size_t i;
> +@@ -228,6 +313,39 @@ static int cgi_pid_del(server *srv, plugin_data *p, pid_t pid) {
> + return 0;
> + }
> +
> ++
> ++static void cgi_ctx_add(plugin_data *p, handler_ctx *hctx) {
> ++ buffer_ctx_t *r = &(p->cgi_ctx);
> ++
> ++ if (r->size == 0) {
> ++ r->size = 16;
> ++ r->hctx = malloc(sizeof(*r->hctx) * r->size);
> ++ } else if (r->used == r->size) {
> ++ r->size += 16;
> ++ r->hctx = realloc(r->hctx, sizeof(*r->hctx) * r->size);
> ++ }
> ++
> ++ r->hctx[r->used++] = hctx;
> ++}
> ++
> ++static void cgi_ctx_del(plugin_data *p, handler_ctx *hctx) {
> ++ size_t i;
> ++ buffer_ctx_t *r = &(p->cgi_ctx);
> ++
> ++ for (i = 0; i < r->used; i++) {
> ++ if (r->hctx[i] == hctx) break;
> ++ }
> ++
> ++ if (i != r->used) {
> ++ /* found */
> ++
> ++ if (i != r->used - 1) {
> ++ r->hctx[i] = r->hctx[r->used - 1];
> ++ }
> ++ r->used--;
> ++ }
> ++}
> ++
> + static int cgi_response_parse(server *srv, connection *con, plugin_data *p, buffer *in) {
> + char *ns;
> + const char *s;
> +@@ -378,6 +496,13 @@ static int cgi_demux_response(server *srv, handler_ctx *hctx) {
> +
> + hctx->response->ptr[n] = '\0';
> + hctx->response->used = n+1;
> ++#ifdef DEBUG
> ++ sprintf(msgbuf, "n=%d, bytes_out=%llu, bytes_in=%llu", n,
> ++ (unsigned long long)con->write_queue->bytes_out,
> ++ (unsigned long long)con->write_queue->bytes_in);
> ++ log_error_write(srv, __FILE__, __LINE__, "ss",
> ++ "(debug) read,", msgbuf);
> ++#endif
> +
> + /* split header from body */
> +
> +@@ -502,8 +627,20 @@ static int cgi_demux_response(server *srv, handler_ctx *hctx) {
> + }
> + } else {
> + http_chunk_append_mem(srv, con, hctx->response->ptr, hctx->response->used);
> ++#ifdef DEBUG
> ++ sprintf(msgbuf, "n=%d, bytes_out=%llu, bytes_in=%llu, limit=%llu", n,
> ++ (unsigned long long)con->write_queue->bytes_out,
> ++ (unsigned long long)con->write_queue->bytes_in,
> ++ (unsigned long long)hctx->high_waterlevel);
> ++ log_error_write(srv, __FILE__, __LINE__,
> ++ "ss", "(debug) append,", msgbuf);
> ++#endif
> + joblist_append(srv, con);
> +- }
> ++ cgi_throttling_control(srv, hctx);
> ++ if (hctx->throttling) {
> ++ return FDEVENT_HANDLED_NOT_FINISHED;
> ++ }
> ++ }
> +
> + #if 0
> + log_error_write(srv, __FILE__, __LINE__, "ddss", con->fd, hctx->fd, connection_get_state(con->state), b->ptr);
> +@@ -552,8 +689,9 @@ static handler_t cgi_connection_close(server *srv, handler_ctx *hctx) {
> + con->plugin_ctx[p->id] = NULL;
> +
> + /* is this a good idea ? */
> +- cgi_handler_ctx_free(hctx);
> +-
> ++ cgi_ctx_del(p, hctx);
> ++ cgi_handler_ctx_free(srv, hctx);
> ++
> + /* if waitpid hasn't been called by response.c yet, do it here */
> + if (pid) {
> + /* check if the CGI-script is already gone */
> +@@ -1156,7 +1294,8 @@ static int cgi_create_env(server *srv, connection *con, plugin_data *p, buffer *
> + con->mode = p->id;
> + buffer_reset(con->physical.path);
> +
> +- hctx = cgi_handler_ctx_init();
> ++ hctx = cgi_handler_ctx_init(p);
> ++ cgi_ctx_add(p, hctx);
> +
> + hctx->remote_conn = con;
> + hctx->plugin_data = p;
> +@@ -1165,6 +1304,11 @@ static int cgi_create_env(server *srv, connection *con, plugin_data *p, buffer *
> + hctx->fde_ndx = -1;
> +
> + con->plugin_ctx[p->id] = hctx;
> ++#ifdef DEBUG
> ++ sprintf(msgbuf, "hctx=%p, con=%p", (void*)hctx, (void*)con);
> ++ log_error_write(srv, __FILE__, __LINE__, "ss",
> ++ "(debug) hctx generated, ", msgbuf);
> ++#endif
> +
> + fdevent_register(srv->ev, hctx->fd, cgi_handle_fdevent, hctx);
> + fdevent_event_set(srv->ev, &(hctx->fde_ndx), hctx->fd, FDEVENT_IN);
> +@@ -1179,7 +1323,8 @@ static int cgi_create_env(server *srv, connection *con, plugin_data *p, buffer *
> +
> + close(hctx->fd);
> +
> +- cgi_handler_ctx_free(hctx);
> ++ cgi_ctx_del(p, hctx);
> ++ cgi_handler_ctx_free(srv, hctx);
> +
> + con->plugin_ctx[p->id] = NULL;
> +
> +@@ -1204,6 +1349,8 @@ static int mod_cgi_patch_connection(server *srv, connection *con, plugin_data *p
> +
> + PATCH(cgi);
> + PATCH(execute_x_only);
> ++ PATCH(high_waterlevel);
> ++ PATCH(low_waterlevel);
> +
> + /* skip the first, the global context */
> + for (i = 1; i < srv->config_context->used; i++) {
> +@@ -1221,6 +1368,10 @@ static int mod_cgi_patch_connection(server *srv, connection *con, plugin_data *p
> + PATCH(cgi);
> + } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("cgi.execute-x-only"))) {
> + PATCH(execute_x_only);
> ++ } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("cgi.high-waterlevel"))) {
> ++ PATCH(high_waterlevel);
> ++ } else if (buffer_is_equal_string(du->key, CONST_STR_LEN("cgi.low-waterlevel"))) {
> ++ PATCH(low_waterlevel);
> + }
> + }
> + }
> +@@ -1273,6 +1424,21 @@ URIHANDLER_FUNC(cgi_is_handled) {
> + TRIGGER_FUNC(cgi_trigger) {
> + plugin_data *p = p_d;
> + size_t ndx;
> ++
> ++ for (ndx = 0; ndx < p->cgi_ctx.used; ndx++) {
> ++ handler_ctx *hctx = p->cgi_ctx.hctx[ndx];
> ++#ifdef DEBUG
> ++ connection *con = hctx->remote_conn;
> ++
> ++ sprintf(msgbuf, "hctx=%p, con=%p, bytes_in_buffer=%llu",
> ++ (void*)hctx, (void*)con,
> ++ (unsigned long long)hctx->bytes_in_buffer);
> ++ log_error_write(srv, __FILE__, __LINE__, "ss",
> ++ "(debug) found using ctx,", msgbuf);
> ++#endif
> ++ cgi_throttling_control(srv, hctx);
> ++ }
> ++
> + /* the trigger handle only cares about lonely PID which we have to wait for */
> + #ifndef __WIN32
> +
> +@@ -1381,7 +1547,8 @@ SUBREQUEST_FUNC(mod_cgi_handle_subrequest) {
> + log_error_write(srv, __FILE__, __LINE__, "sds", "cgi close failed ", hctx->fd, strerror(errno));
> + }
> +
> +- cgi_handler_ctx_free(hctx);
> ++ cgi_ctx_del(p, hctx);
> ++ cgi_handler_ctx_free(srv, hctx);
> +
> + con->plugin_ctx[p->id] = NULL;
> +
> +@@ -1413,7 +1580,8 @@ SUBREQUEST_FUNC(mod_cgi_handle_subrequest) {
> + log_error_write(srv, __FILE__, __LINE__, "sds", "cgi close failed ", hctx->fd, strerror(errno));
> + }
> +
> +- cgi_handler_ctx_free(hctx);
> ++ cgi_ctx_del(p, hctx);
> ++ cgi_handler_ctx_free(srv, hctx);
> +
> + con->plugin_ctx[p->id] = NULL;
> + return HANDLER_FINISHED;
> +--
> +1.8.4.2
> +
> diff --git a/meta/recipes-extended/lighttpd/lighttpd_1.4.35.bb b/meta/recipes-extended/lighttpd/lighttpd_1.4.35.bb
> index 0cf5aa2..d3888e6 100644
> --- a/meta/recipes-extended/lighttpd/lighttpd_1.4.35.bb
> +++ b/meta/recipes-extended/lighttpd/lighttpd_1.4.35.bb
> @@ -24,6 +24,7 @@ SRC_URI = "http://download.lighttpd.net/lighttpd/releases-1.4.x/lighttpd-${PV}.t
> file://lighttpd \
> file://lighttpd.service \
> file://pkgconfig.patch \
> + file://0001-mod_cgi-buffers-data-without-bound.patch \
> "
>
> SRC_URI[md5sum] = "f7a88130ee9984b421ad8aa80629750a"
> --
> 1.8.4.2
>
> --
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