[nginx] Fixed segfault with try_files introduced by c985d90a8d1f.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/4bc94faeff66
branches:  
changeset: 6226:4bc94faeff66
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Sun Aug 16 10:51:16 2015 +0300
description:
Fixed segfault with try_files introduced by c985d90a8d1f.

If alias was used in a location given by a regular expression,
nginx used to do wrong thing in try_files if a location name (i.e.,
regular expression) was an exact prefix of URI.  The following
configuration triggered a segmentation fault on a request to "/mail":

    location ~ /mail {
        alias /path/to/directory;
        try_files $uri =404;
    }

Reported by Per Hansson.

diffstat:

 src/http/ngx_http_core_module.c |  4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diffs (14 lines):

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -1239,7 +1239,9 @@ ngx_http_core_try_files_phase(ngx_http_r
 
             *e.pos = '\0';
 
-            if (alias && ngx_strncmp(name, clcf->name.data, alias) == 0) {
+            if (alias && alias != NGX_MAX_SIZE_T_VALUE
+                && ngx_strncmp(name, clcf->name.data, alias) == 0)
+            {
                 ngx_memmove(name, name + alias, len - alias);
                 path.len -= alias;
             }