[nginx] Cache: reset c->body_start when reading a variant on Vary mismatch.

[Sergey Kandaurov]

details:   https://hg.nginx.org/nginx/rev/847fd35f94de
branches:  
changeset: 7704:847fd35f94de
user:      Sergey Kandaurov <pluknet at nginx.com>
date:      Fri Aug 04 19:37:37 2017 +0300
description:
Cache: reset c->body_start when reading a variant on Vary mismatch.

Previously, a variant not present in shared memory and stored on disk using a
secondary key was read using c->body_start from a variant stored with a main
key.  This could result in critical errors "cache file .. has too long header".

diffstat:

 src/http/ngx_http_cache.h      |  1 +
 src/http/ngx_http_file_cache.c |  4 +++-
 2 files changed, 4 insertions(+), 1 deletions(-)

diffs (32 lines):

diff -r da5e3f5b1673 -r 847fd35f94de src/http/ngx_http_cache.h
--- a/src/http/ngx_http_cache.h	Wed Sep 02 23:13:36 2020 +0300
+++ b/src/http/ngx_http_cache.h	Fri Aug 04 19:37:37 2017 +0300
@@ -80,6 +80,7 @@ struct ngx_http_cache_s {
     ngx_str_t                        vary;
     u_char                           variant[NGX_HTTP_CACHE_KEY_LEN];
 
+    size_t                           buffer_size;
     size_t                           header_start;
     size_t                           body_start;
     off_t                            length;
diff -r da5e3f5b1673 -r 847fd35f94de src/http/ngx_http_file_cache.c
--- a/src/http/ngx_http_file_cache.c	Wed Sep 02 23:13:36 2020 +0300
+++ b/src/http/ngx_http_file_cache.c	Fri Aug 04 19:37:37 2017 +0300
@@ -294,6 +294,8 @@ ngx_http_file_cache_open(ngx_http_reques
         cln->data = c;
     }
 
+    c->buffer_size = c->body_start;
+
     rc = ngx_http_file_cache_exists(cache, c);
 
     ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
@@ -1230,7 +1232,7 @@ ngx_http_file_cache_reopen(ngx_http_requ
 
     c->secondary = 1;
     c->file.name.len = 0;
-    c->body_start = c->buf->end - c->buf->start;
+    c->body_start = c->buffer_size;
 
     ngx_memcpy(c->key, c->variant, NGX_HTTP_CACHE_KEY_LEN);