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git/worktree-fix-worktree-add-race.patch

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From e134801d570d0a0c85424eb80b41893f4d8383ca Mon Sep 17 00:00:00 2001
From: Michal Suchanek <msuchanek@suse.de>
Date: Wed, 13 Feb 2019 10:40:42 +0100
Subject: [PATCH] worktree: fix worktree add race.
Git runs a stat loop to find a worktree name that's available and then does
mkdir on the found name. Turn it to mkdir loop to avoid another invocation of
worktree add finding the same free name and creating the directory first.
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
v2:
- simplify loop exit condition
- exit early if the mkdir fails for reason other than already present
worktree
- make counter unsigned
---
builtin/worktree.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 3f9907fcc994..85a604cfe98c 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -268,10 +268,10 @@ static int add_worktree(const char *path, const char *refname,
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 @@ static int add_worktree(const char *path, const char *refname,
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 @@ static int add_worktree(const char *path, const char *refname,
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;
--
2.20.1