[PATCH] Fixed crash protection in round robin

[Maxim Dounin]

Hello!

On Tue, Dec 20, 2022 at 04:16:37PM +0800, 乔志奇 wrote:

> # HG changeset patch
> # User 乔志奇@Matebook-Qiao <qiaozhiqi2016 at gmail.com>
> # Date 1671521412 -28800
> #      Tue Dec 20 15:30:12 2022 +0800
> # Branch nginx-bugfix-crash
> # Node ID 992013158c8970318c20e2e3294dbc9311bb20c8
> # Parent  3108d4d668e4b907868b815f0441d4c893bf4188
> Fixed crash protection in round robin
> 
> When all servers in the upstream are in the down state, rrp->peers will be
> NULL, initialization will crash here, and protection is needed.
> 
> diff -r 3108d4d668e4 -r 992013158c89
> src/http/ngx_http_upstream_round_robin.c
> --- a/src/http/ngx_http_upstream_round_robin.c  Fri Dec 16 01:15:15 2022
> +0400
> +++ b/src/http/ngx_http_upstream_round_robin.c  Tue Dec 20 15:30:12 2022
> +0800
> @@ -275,6 +275,10 @@
>      rrp->current = NULL;
>      rrp->config = 0;
> 
> +    if (rrp->peers == NULL) {
> +        return NGX_ERROR;
> +    }
> +
>      n = rrp->peers->number;
> 
>      if (rrp->peers->next && rrp->peers->next->number > n) {

Could you please clarify how rrp->peers can be NULL here?  An 
example configuration and/or test which demonstrates the problem 
would be awesome.  Thanks in advance.

-- 
Maxim Dounin
http://mdounin.ru/