real_path: remove unsafe API

Returning a shared buffer invites very subtle bugs due to reentrancy or
multi-threading, as demonstrated by the previous patch.

There was an unfinished effort to abolish this [1].

Let's finally rid of `real_path()`, using `strbuf_realpath()` instead.

This patch uses a local `strbuf` for most places where `real_path()` was
previously called.

However, two places return the value of `real_path()` to the caller. For
them, a `static` local `strbuf` was added, effectively pushing the
problem one level higher:
    read_gitfile_gently()
    get_superproject_working_tree()

[1] https://lore.kernel.org/git/1480964316-99305-1-git-send-email-bmwill@google.com/

Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Alexandr Miloslavskiy
2020-03-10 13:11:22 +00:00
committed by Junio C Hamano
parent 0915a5b4cd
commit 3d7747e318
13 changed files with 59 additions and 24 deletions

View File

@ -420,6 +420,7 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
struct dir_iterator *iter;
int iter_status;
unsigned int flags;
struct strbuf realpath = STRBUF_INIT;
mkdir_if_missing(dest->buf, 0777);
@ -454,7 +455,8 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
if (unlink(dest->buf) && errno != ENOENT)
die_errno(_("failed to unlink '%s'"), dest->buf);
if (!option_no_hardlinks) {
if (!link(real_path(src->buf), dest->buf))
strbuf_realpath(&realpath, src->buf, 1);
if (!link(realpath.buf, dest->buf))
continue;
if (option_local > 0)
die_errno(_("failed to create link '%s'"), dest->buf);
@ -468,6 +470,8 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
strbuf_setlen(src, src_len);
die(_("failed to iterate over '%s'"), src->buf);
}
strbuf_release(&realpath);
}
static void clone_local(const char *src_repo, const char *dest_repo)