tree 1f18de9d677f480cfd8882106c27d2d7ecf4a420
parent 98f9bac58ef5d9fdd5c9e5ea6f8e28c3968c5276
author Maxim Dounin <mdounin@mdounin.ru> 1464660810 +0300
committer Maxim Dounin <mdounin@mdounin.ru> 1464660810 +0300

Core: skip special buffers on writing (ticket #981).

A special last buffer with cl->buf->pos set to NULL can be present in
a chain when writing request body if chunked encoding was used.  This
resulted in a NULL pointer dereference if it happened to be the only
buffer left after a do...while loop iteration in ngx_write_chain_to_file().

The problem originally appeared in nginx 1.3.9 with chunked encoding
support.  Additionally, rev. 3832b608dc8d (nginx 1.9.13) changed the
minimum number of buffers to trigger this from IOV_MAX (typically 1024)
to NGX_IOVS_PREALLOCATE (typically 64).

Fix is to skip such buffers in ngx_chain_to_iovec(), much like it is
done in other places.