Re: PATCH] bisect--helper: plug strvec leak in bisect_start()
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Oct 5, 2022, 07:29 UTC
- Message-ID
- <221005.8635c2u3k5.gmgdl@evledraar.gmail.com>
- In-Reply-To
- <5c6a4c30-d454-51b6-ec57-9af036b9c4e0@web.de>
On Tue, Oct 04 2022, René Scharfe wrote:
Show 31 quoted lines
> The strvec "argv" is used to build a command for run_command_v_opt(),
> but never freed. Use the "args" strvec of struct child_process and
> run_command() instead, which releases the allocated memory both on
> success and on error. We just also need to set the "git_cmd" bit
> directly.
>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
> builtin/bisect--helper.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 501245fac9..9fe0c08479 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -765,11 +765,12 @@ static enum bisect_error bisect_start(struct bisect_terms *terms, const char **a
> strbuf_read_file(&start_head, git_path_bisect_start(), 0);
> strbuf_trim(&start_head);
> if (!no_checkout) {
> - struct strvec argv = STRVEC_INIT;
> + struct child_process cmd = CHILD_PROCESS_INIT;
>
> - strvec_pushl(&argv, "checkout", start_head.buf,
> + cmd.git_cmd = 1;
> + strvec_pushl(&cmd.args, "checkout", start_head.buf,
> "--", NULL);
> - if (run_command_v_opt(argv.v, RUN_GIT_CMD)) {
> + if (run_command(&cmd)) {
> res = error(_("checking out '%s' failed."
> " Try 'git bisect start "
> "<valid-branch>'."),Okey, so we leak the strvec, and instead of adding a strvec_clear() you're just switching the lower-level API, which we'd need in some cases with this API, and would often be cleaner.
But I don't get it in this case, why not just:
diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 4e97817fba5..f9645a9d0df 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -763,11 +763,9 @@ static enum bisect_error bisect_start(struct bisect_terms *terms, const char **a
strbuf_read_file(&start_head, git_path_bisect_start(), 0);
strbuf_trim(&start_head);
if (!no_checkout) {
- struct strvec argv = STRVEC_INIT;
+ const char *argv[] = { "checkout", start_head.buf, "--", NULL };
- strvec_pushl(&argv, "checkout", start_head.buf,
- "--", NULL);
- if (run_command_v_opt(argv.v, RUN_GIT_CMD)) {
+ if (run_command_v_opt(argv, RUN_GIT_CMD)) {
res = error(_("checking out '%s' failed."
" Try 'git bisect start "
"<valid-branch>'."),The common pattern for run_command_v_opt() callers that don't need a
dynamic list is exactly that, e.g.:
builtin/difftool.c=static int print_tool_help(void)
builtin/difftool.c-{
builtin/difftool.c- const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
builtin/difftool.c: return run_command_v_opt(argv, RUN_GIT_CMD);
builtin/difftool.c-}
And:
fsmonitor-ipc.c=static int spawn_daemon(void)
fsmonitor-ipc.c-{
fsmonitor-ipc.c- const char *args[] = { "fsmonitor--daemon", "start", NULL };
fsmonitor-ipc.c-
fsmonitor-ipc.c: return run_command_v_opt_tr2(args, RUN_COMMAND_NO_STDIN | RUN_GIT_CMD,
fsmonitor-ipc.c- "fsmonitor");
fsmonitor-ipc.c-}Here we have the "start_head" which we'll need to strbuf_release(), but we're not returning directly, and the function is doing that already.
Your version is slightly more memory efficient, i.e. we'll end up having to push this to a "struct child_process"'s argv anyway, but this is less code & we don't need to carefully eyeball run_command_v_opt_cd_env_tr2() to see that it's correct (which I did, your version does the right thing too).