Backported for 5.4 from:

From c69bcb212b37900fd61daaf38762e4974cb4dcc9 Mon Sep 17 00:00:00 2001

From: Jakub Zelenka <bukka@php.net>

Date: Sat, 12 Oct 2019 15:56:16 +0100

Subject: [PATCH 1/2] Fix bug #78599 (env_path_info underflow can lead to RCE)

 (CVE-2019-11043)

cheery-picked from ab061f95ca966731b1c84cf5b7b20155c0a1c06a

without the test as tester not available

---

 sapi/fpm/fpm/fpm_main.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sapi/fpm/fpm/fpm_main.c b/sapi/fpm/fpm/fpm_main.c

index d12ac01859..22b889c167 100644

--- a/sapi/fpm/fpm/fpm_main.c

+++ b/sapi/fpm/fpm/fpm_main.c

@@ -1210,8 +1210,8 @@ static void init_request_info(TSRMLS_D)

 								path_info = script_path_translated + ptlen;

 								tflag = (slen != 0 && (!orig_path_info || strcmp(orig_path_info, path_info) != 0));

 							} else {

-								path_info = env_path_info ? env_path_info + pilen - slen : NULL;

-								tflag = (orig_path_info != path_info);

+								path_info = (env_path_info && pilen > slen) ? env_path_info + pilen - slen : NULL;

+								tflag = path_info && (orig_path_info != path_info);

 							}

 							if (tflag) {