bugfix: wip: Set headers in the tail of a list rather than in the head #2182
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It seems that ngx_http_variable_headers_internal function in nginx/src/http/ngx_http_variables.c relies on the fact that the last header values is stored in the last element of a list. Therefore we should avoid changing a random element in the head of a list of headers and either change the last element or add a new element to the list.
oxpa
changed the title
ssdr
reviewed
Apr 23, 2023
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| h = *headers; | ||
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| if (h->hash == 0) { |
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Oh no, I'm afraid here h is NULL ptr after last for loop iterate...
ssdr
reviewed
Apr 23, 2023
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| for (ph = headers; *ph; ph = &(*ph)->next) { /* void */ } | ||
| } else { | ||
| ho = ngx_list_push(&r->headers_out.headers); |
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when last element is valid and other elements are not, here will make a new element, right? Does it mean that the invalid elements never be reused in pool? So why not just nullifying the first element next for simplicity?
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Actually when set builtin multi input header, it just nullifying the next pointer.
can we do same thing for output headers?
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It seems that ngx_http_variable_headers_internal function in nginx/src/http/ngx_http_variables.c relies on the fact that the last header values is stored in the last element of a list. Therefore we should avoid changing a random element in the head of a list of headers and either change the last element or add a new element to the list.
Not sure if this is the proper fix.
Thanks to @ssdr for pointing out the problem in #2177
I hereby granted the copyright of the changes in this pull request
to the authors of this lua-nginx-module project.