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Upstream: fixed running posted requests (ticket #788).

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Previously, the upstream resolve handler always called
ngx_http_run_posted_requests() to run posted requests after processing the
resolver response.  However, if the handler was called directly from the
ngx_resolve_name() function (for example, if the resolver response was cached),
running posted requests from the handler could lead to the following errors:

- If the request was scheduled for termination, it could actually be terminated
in the resolve handler.  Upper stack frames could reference the freed request
object in this case.

- If a significant number of requests were posted, and for each of them the
resolve handler was called directly from the ngx_resolve_name() function,
posted requests could be run recursively and lead to stack overflow.

Now ngx_http_run_posted_requests() is only called from asynchronously invoked
resolve handlers.
This commit is contained in:
Roman Arutyunyan 2017-06-14 20:13:41 +03:00
parent 439e205255
commit efa61f42c1
1 changed files with 6 additions and 1 deletions
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7
src/http/ngx_http_upstream.c
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@ -1143,11 +1143,14 @@ ngx_http_upstream_cache_check_range(ngx_http_request_t *r,
static void
ngx_http_upstream_resolve_handler(ngx_resolver_ctx_t *ctx)
{
ngx_uint_t run_posted;
ngx_connection_t *c;
ngx_http_request_t *r;
ngx_http_upstream_t *u;
ngx_http_upstream_resolved_t *ur;
run_posted = ctx->async;
r = ctx->data;
c = r->connection;
@ -1211,7 +1214,9 @@ ngx_http_upstream_resolve_handler(ngx_resolver_ctx_t *ctx)
failed:
ngx_http_run_posted_requests(c);
if (run_posted) {
ngx_http_run_posted_requests(c);
}
}