From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 9 Apr 2019 17:14:24 +0000 (+0900)
Subject: Merge branch 'ms/worktree-add-atomic-mkdir'
X-Git-Tag: v2.22.0-rc0~126
X-Git-Url: https://git.lorimer.id.au/gitweb.git/diff_plain/20fe798b1bf301f78485a56381ad8dad48b2c670?ds=inline;hp=-c

Merge branch 'ms/worktree-add-atomic-mkdir'

"git worktree add" used to do a "find an available name with stat
and then mkdir", which is race-prone.  This has been fixed by using
mkdir and reacting to EEXIST in a loop.

* ms/worktree-add-atomic-mkdir:
worktree: fix worktree add race
---

20fe798b1bf301f78485a56381ad8dad48b2c670
diff --combined builtin/worktree.c
index 6cc094a453,85a604cfe9..d2a7e2f3f1
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@@ -268,10 -268,10 +268,10 @@@ static int add_worktree(const char *pat
  	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
  	struct strbuf sb = STRBUF_INIT;
  	const char *name;
- 	struct stat st;
  	struct child_process cp = CHILD_PROCESS_INIT;
  	struct argv_array child_env = ARGV_ARRAY_INIT;
- 	int counter = 0, len, ret;
+ 	unsigned int counter = 0;
+ 	int len, ret;
  	struct strbuf symref = STRBUF_INIT;
  	struct commit *commit = NULL;
  	int is_branch = 0;
@@@ -295,8 -295,12 +295,12 @@@
  	if (safe_create_leading_directories_const(sb_repo.buf))
  		die_errno(_("could not create leading directories of '%s'"),
  			  sb_repo.buf);
- 	while (!stat(sb_repo.buf, &st)) {
+ 
+ 	while (mkdir(sb_repo.buf, 0777)) {
  		counter++;
+ 		if ((errno != EEXIST) || !counter /* overflow */)
+ 			die_errno(_("could not create directory of '%s'"),
+ 				  sb_repo.buf);
  		strbuf_setlen(&sb_repo, len);
  		strbuf_addf(&sb_repo, "%d", counter);
  	}
@@@ -306,8 -310,6 +310,6 @@@
  	atexit(remove_junk);
  	sigchain_push_common(remove_junk_on_signal);
  
- 	if (mkdir(sb_repo.buf, 0777))
- 		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
  	junk_git_dir = xstrdup(sb_repo.buf);
  	is_junk = 1;
  
@@@ -402,7 -404,6 +404,7 @@@ done
  			cp.dir = path;
  			cp.env = env;
  			cp.argv = NULL;
 +			cp.trace2_hook_name = "post-checkout";
  			argv_array_pushl(&cp.args, absolute_path(hook),
  					 oid_to_hex(&null_oid),
  					 oid_to_hex(&commit->object.oid),