[PATCH] Fixing buffer over-read when accepting unix domain sockets

[Yichun Zhang (agentzh)]

Hello!

I've found a heap buffer over-read issue in the Nginx core via clang's
AddressSanitizer tool when Nginx is accepting a unix domain socket in
ngx_event_accept.

At least on Linux, accept and accept4 syscalls always return a socket
length of 2 for unix domain sockets, which makes later accesses to
saun->sun_path in function ngx_sock_ntop invalid (because
sizeof(sa->sa_family) == sizeof(short) == 2).

The patch attached fixes this issue.

Thanks!
-agentzh

--- nginx-1.4.1/src/event/ngx_event_accept.c 2013-05-06 03:26:50.000000000 -0700
+++ nginx-1.4.1-patched/src/event/ngx_event_accept.c 2013-07-09
17:41:42.688468839 -0700
@@ -268,7 +268,7 @@ ngx_event_accept(ngx_event_t *ev)
         wev->own_lock = &c->lock;
 #endif

-        if (ls->addr_ntop) {
+        if (ls->addr_ntop && socklen > sizeof(c->sockaddr->sa_family)) {
             c->addr_text.data = ngx_pnalloc(c->pool, ls->addr_text_max_len);
             if (c->addr_text.data == NULL) {
                 ngx_close_accepted_connection(c);
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