fix race condition if during reconfiguration two cache managers try

to delete old inactive entries: one of them removes a entry just locked by
other manager from the queue and the rbtree as long inactive entry,
causes the latter manager to segfault leaving cache mutex locked,
the bug has been introduced in r3727

2 files changed, 10 insertions, 1 deletions

diff --git a/src/http/ngx_http_cache.h b/src/http/ngx_http_cache.h
index 1a23e4620..b511a0b91 100644
--- a/src/http/ngx_http_cache.h
+++ b/src/http/ngx_http_cache.h
@@ -43,7 +43,8 @@ typedef struct {
     unsigned                         error:10;
     unsigned                         exists:1;
     unsigned                         updating:1;
-                                     /* 12 unused bits */
+    unsigned                         deleting:1;
+                                     /* 11 unused bits */
 
     ngx_file_uniq_t                  uniq;
     time_t                           expire;
diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
index d14a7c5e6..0d97e94ec 100644
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -582,6 +582,7 @@ ngx_http_file_cache_exists(ngx_http_file_cache_t *cache, ngx_http_cache_t *c)
     fcn->uses = 1;
     fcn->count = 1;
     fcn->updating = 0;
+    fcn->deleting = 0;
 
 renew:
 
@@ -1102,6 +1103,10 @@ ngx_http_file_cache_expire(ngx_http_file_cache_t *cache)
             continue;
         }
 
+        if (fcn->deleting) {
+            continue;
+        }
+
         p = ngx_hex_dump(key, (u_char *) &fcn->node.key,
                          sizeof(ngx_rbtree_key_t));
         len = NGX_HTTP_CACHE_KEY_LEN - sizeof(ngx_rbtree_key_t);
@@ -1153,6 +1158,7 @@ ngx_http_file_cache_delete(ngx_http_file_cache_t *cache, ngx_queue_t *q,
         *p = '\0';
 
         fcn->count++;
+        fcn->deleting = 1;
         ngx_shmtx_unlock(&cache->shpool->mutex);
 
         len = path->name.len + 1 + path->len + 2 * NGX_HTTP_CACHE_KEY_LEN;
@@ -1168,6 +1174,7 @@ ngx_http_file_cache_delete(ngx_http_file_cache_t *cache, ngx_queue_t *q,
 
         ngx_shmtx_lock(&cache->shpool->mutex);
         fcn->count--;
+        fcn->deleting = 0;
     }
 
     if (fcn->count == 0) {
@@ -1431,6 +1438,7 @@ ngx_http_file_cache_add(ngx_http_file_cache_t *cache, ngx_http_cache_t *c)
         fcn->error = 0;
         fcn->exists = 1;
         fcn->updating = 0;
+        fcn->deleting = 0;
         fcn->uniq = c->uniq;
         fcn->valid_sec = c->valid_sec;
         fcn->body_start = c->body_start;