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

@ -54,7 +54,8 @@ static int launch_specified_editor(const char *editor, const char *path,
return error("Terminal is dumb, but EDITOR unset");
if (strcmp(editor, ":")) {
const char *args[] = { editor, real_path(path), NULL };
struct strbuf realpath = STRBUF_INIT;
const char *args[] = { editor, NULL, NULL };
struct child_process p = CHILD_PROCESS_INIT;
int ret, sig;
int print_waiting_for_editor = advice_waiting_for_editor && isatty(2);
@ -75,16 +76,22 @@ static int launch_specified_editor(const char *editor, const char *path,
fflush(stderr);
}
strbuf_realpath(&realpath, path, 1);
args[1] = realpath.buf;
p.argv = args;
p.env = env;
p.use_shell = 1;
p.trace2_child_class = "editor";
if (start_command(&p) < 0)
if (start_command(&p) < 0) {
strbuf_release(&realpath);
return error("unable to start editor '%s'", editor);
}
sigchain_push(SIGINT, SIG_IGN);
sigchain_push(SIGQUIT, SIG_IGN);
ret = finish_command(&p);
strbuf_release(&realpath);
sig = ret - 128;
sigchain_pop(SIGINT);
sigchain_pop(SIGQUIT);