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Upstream: fixed "header already sent" alerts on backend errors.

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Following ad3f342f14ba046c (1.9.13), it is possible that a request where
header was already sent will be finalized with NGX_HTTP_BAD_GATEWAY,
triggering an attempt to return additional error response and the
"header already sent" alert as a result.

In particular, it is trivial to reproduce the problem with a HEAD request
and caching enabled.  With caching enabled nginx will change HEAD to GET
and will set u->pipe->downstream_error to suppress sending the response
body to the client.  When a backend-related error occurs (for example,
proxy_read_timeout expires), ngx_http_finalize_upstream_request() will
be called with NGX_HTTP_BAD_GATEWAY.  After ad3f342f14ba046c this will
result in ngx_http_finalize_request(NGX_HTTP_BAD_GATEWAY).

Fix is to move u->pipe->downstream_error handling to a later point,
where all special response codes are changed to NGX_ERROR.

Reported by Jan Prachar,
http://mailman.nginx.org/pipermail/nginx-devel/2018-January/010737.html.
This commit is contained in:
Maxim Dounin 2018-01-11 21:43:49 +03:00
parent 9b81d3b1bb
commit 3377c00119
1 changed files with 4 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
src/http/ngx_http_upstream.c
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@ -4374,8 +4374,7 @@ ngx_http_upstream_finalize_request(ngx_http_request_t *r,
if (!u->header_sent
|| rc == NGX_HTTP_REQUEST_TIME_OUT
|| rc == NGX_HTTP_CLIENT_CLOSED_REQUEST
|| (u->pipe && u->pipe->downstream_error))
|| rc == NGX_HTTP_CLIENT_CLOSED_REQUEST)
{
ngx_http_finalize_request(r, rc);
return;
@ -4388,7 +4387,9 @@ ngx_http_upstream_finalize_request(ngx_http_request_t *r,
flush = 1;
}
if (r->header_only) {
if (r->header_only
|| (u->pipe && u->pipe->downstream_error))
{
ngx_http_finalize_request(r, rc);
return;
}