From: Maxim Dounin <mdounin@mdounin.ru>
Date: Tue, 17 Oct 2017 16:52:16 +0000 (+0300)
Subject: Core: free shared memory zones only after reconfiguration.
X-Git-Tag: release-1.13.7~7
X-Git-Url: http://www.kaiwu.me/postgresql/commit/?a=commitdiff_plain;h=9cb9ce78b1d81ccdbcd123ccc3dab295b836a174;p=nginx.git

Core: free shared memory zones only after reconfiguration.

This is what usually happens for zones no longer used in the new
configuration, but zones where size or tag were changed were freed
when creating new memory zones.  If reconfiguration failed (for
example, due to a conflicting listening socket), this resulted in a
segmentation fault in the master process.

Reported by Zhihua Cao,
http://mailman.nginx.org/pipermail/nginx-devel/2017-October/010536.html.
---

diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
index 675a50614..f3ac24d7a 100644
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -470,8 +470,6 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
                 goto shm_zone_found;
             }
 
-            ngx_shm_free(&oshm_zone[n].shm);
-
             break;
         }
 
@@ -662,14 +660,26 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
                 n = 0;
             }
 
-            if (oshm_zone[i].shm.name.len == shm_zone[n].shm.name.len
-                && ngx_strncmp(oshm_zone[i].shm.name.data,
-                               shm_zone[n].shm.name.data,
-                               oshm_zone[i].shm.name.len)
-                == 0)
+            if (oshm_zone[i].shm.name.len != shm_zone[n].shm.name.len) {
+                continue;
+            }
+
+            if (ngx_strncmp(oshm_zone[i].shm.name.data,
+                            shm_zone[n].shm.name.data,
+                            oshm_zone[i].shm.name.len)
+                != 0)
+            {
+                continue;
+            }
+
+            if (oshm_zone[i].tag == shm_zone[n].tag
+                && oshm_zone[i].shm.size == shm_zone[n].shm.size
+                && !oshm_zone[i].noreuse)
             {
                 goto live_shm_zone;
             }
+
+            break;
         }
 
         ngx_shm_free(&oshm_zone[i].shm);