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[PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Maxim Dounin
November 26, 2023 10:10PM
# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1701049758 -10800
# Mon Nov 27 04:49:18 2023 +0300
# Node ID faf0b9defc76b8683af466f8a950c2c241382970
# Parent a5e39e9d1f4c84dcbe6a2f9e079372a3d63aef0b
Upstream: fixed usage of closed sockets with filter finalization.

When filter finalization is triggered when working with an upstream server,
and error_page redirects request processing to some simple handler,
ngx_http_request_finalize() triggers request termination when the response
is sent. In particular, via the upstream cleanup handler, nginx will close
the upstream connection and the corresponding socket.

Still, this can happen to be with ngx_event_pipe() on stack. While
the code will set p->downstream_error due to NGX_ERROR returned from the
output filter chain by filter finalization, otherwise the error will be
ignored till control returns to ngx_http_upstream_process_request().
And event pipe might try reading from the (already closed) socket, resulting
in "readv() failed (9: Bad file descriptor) while reading upstream" errors
(or even segfaults with SSL).

Such errors were seen with the following configuration:

location /t2 {
proxy_pass http://127.0.0.1:8080/big;

image_filter_buffer 10m;
image_filter resize 150 100;
error_page 415 = /empty;
}

location /empty {
return 204;
}

location /big {
# big enough static file
}

Fix is to set p->upstream_error in ngx_http_upstream_finalize_request(),
so the existing checks in ngx_event_pipe_read_upstream() will prevent
further reading from the closed upstream connection.

Similarly, p->upstream_error is now checked when handling events at
ngx_event_pipe() exit, as checking p->upstream->fd is not enough if
keepalive upstream connections are being used and the connection was
saved to cache during request termination.

diff --git a/src/event/ngx_event_pipe.c b/src/event/ngx_event_pipe.c
--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -57,7 +57,9 @@ ngx_event_pipe(ngx_event_pipe_t *p, ngx_
do_write = 1;
}

- if (p->upstream->fd != (ngx_socket_t) -1) {
+ if (p->upstream->fd != (ngx_socket_t) -1
+ && !p->upstream_error)
+ {
rev = p->upstream->read;

flags = (rev->eof || rev->error) ? NGX_CLOSE_EVENT : 0;
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -4561,6 +4561,10 @@ ngx_http_upstream_finalize_request(ngx_h

u->peer.connection = NULL;

+ if (u->pipe) {
+ u->pipe->upstream_error = 1;
+ }
+
if (u->pipe && u->pipe->temp_file) {
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"http upstream temp fd: %d",
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Subject Author Views Posted

[PATCH 0 of 4] aio fixes

Maxim Dounin 446 November 26, 2023 10:10PM

[PATCH 3 of 4] Silenced complaints about socket leaks on forced termination

Maxim Dounin 74 November 26, 2023 10:10PM

Re: [PATCH 3 of 4] Silenced complaints about socket leaks on forced termination

Sergey Kandaurov 67 January 26, 2024 07:28AM

Re: [PATCH 3 of 4] Silenced complaints about socket leaks on forced termination

Maxim Dounin 59 January 29, 2024 02:32AM

[PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Maxim Dounin 83 November 26, 2023 10:10PM

Re: [PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Sergey Kandaurov 57 January 26, 2024 07:28AM

Re: [PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Maxim Dounin 62 January 29, 2024 01:44AM

Re: [PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Sergey Kandaurov 55 January 29, 2024 08:24AM

Re: [PATCH 2 of 4] Upstream: fixed usage of closed sockets with filter finalization

Maxim Dounin 56 January 29, 2024 10:08PM

[PATCH 4 of 4] AIO operations now add timers (ticket #2162)

Maxim Dounin 73 November 26, 2023 10:10PM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

J Carter 57 January 08, 2024 06:28AM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

J Carter 61 January 08, 2024 08:32AM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

Maxim Dounin 65 January 09, 2024 01:00AM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

J Carter 82 January 09, 2024 10:12AM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

Sergey Kandaurov 95 January 26, 2024 07:28AM

Re: [PATCH 4 of 4] AIO operations now add timers (ticket #2162)

Maxim Dounin 57 January 29, 2024 02:32AM

[PATCH 1 of 4] Fixed request termination with AIO and subrequests (ticket #2555)

Maxim Dounin 91 November 26, 2023 10:10PM

Re: [PATCH 1 of 4] Fixed request termination with AIO and subrequests (ticket #2555)

Roman Arutyunyan 57 January 26, 2024 07:04AM

Re: [PATCH 1 of 4] Fixed request termination with AIO and subrequests (ticket #2555)

Maxim Dounin 65 January 29, 2024 03:00AM

Re: [PATCH 1 of 4] Fixed request termination with AIO and subrequests (ticket #2555)

Roman Arutyunyan 72 January 29, 2024 09:10AM

Re: [PATCH 1 of 4] Fixed request termination with AIO and subrequests (ticket #2555)

Maxim Dounin 90 January 29, 2024 10:08PM



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