Resolves segfault in patch command

0001-Updated-output_files-function-to-prevent-segfault.patch

From b0a9156259c1ff9f1a0d42a86e08250e37248a0b Mon Sep 17 00:00:00 2001
From: James Brink <brink.james@gmail.com>
Date: Thu, 27 Dec 2018 04:50:56 -0700
Subject: [PATCH] Updated output_files function to prevent segfault.

I  have updated the output_files function in patch.c to gracefully
handle the following scenario.

Given a git style patch like the following.

  diff --git a/some_file b/some_file
  index 7898192..6178079 100644
  --- a/some_file
  +++ b/some_file
  @@ -1 +1 @@
  -a
  +b

and then running

patch non-existent.file my.patch

will result in a nasty recursion loop that eventually segfaults.
This patch simply addresses the segfault and nothing else, I suspect
some additional work and better error reporting/handling would be
needed.

here is a full example using docker to safely see this bug in action.

docker pull alpine:latest && docker run -i -t alpine:latest sh -c "apk --update add git patch;git config --global user.email 'you@example.com';git config --global user.name 'Your Name';git init;echo 'a' > some_file;git add some_file;git commit -m 'Initial commit';echo -e 'b' > some_file;git diff | patch some_file;"
---
 src/patch.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/patch.c b/src/patch.c
index 81c7a02..c7b6357 100644
--- a/src/patch.c
+++ b/src/patch.c
@@ -1938,9 +1938,11 @@ static void
 output_files (struct stat const *st)
 {
   gl_list_iterator_t iter;
+  gl_list_t files = files_to_output;
   const void *elt;
 
-  iter = gl_list_iterator (files_to_output);
+  init_files_to_output();
+  iter = gl_list_iterator (files);
   while (gl_list_iterator_next (&iter, &elt, NULL))
     {
       const struct file_to_output *file_to_output = elt;
-- 
2.20.1