Fix path_info pointer underflow in CGI fix_pathinfo handling - #250
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When the PATH_INFO supplied by the webserver is shorter than the suffix stripped from SCRIPT_FILENAME, computing env_path_info + pilen - slen underflows and the subsequent path_info[0] = 0 writes out of bounds before the start of the string. The FPM side of this same loop was hardened by commit ab061f9 (CVE-2019-11043) but sapi/cgi was never given the equivalent guard. Mirror it: only derive path_info when pilen exceeds slen, and skip the ORIG_*/SCRIPT_NAME juggling when there is no extracted path.
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Upstream: php#23411 |
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Fix a path_info pointer underflow in the CGI fix_pathinfo strip loop: when PATH_INFO is shorter than the suffix stripped from SCRIPT_FILENAME, env_path_info + pilen - slen underflows and the subsequent path_info[0] write goes out of bounds.