From: Andrzej Hunt <andrzej@ahunt.org>
To: Miriam Rubio <mirucam@gmail.com>, git@vger.kernel.org
Cc: Tanushree Tumane <tanushreetumane@gmail.com>,
Christian Couder <chriscool@tuxfamily.org>
Subject: Re: [PATCH v3 3/4] bisect--helper: reimplement `bisect_run` shell function in C
Date: Tue, 4 May 2021 19:26:01 +0200 [thread overview]
Message-ID: <3771bfc2-e4a4-3c5d-bcf5-673b403358ca@ahunt.org> (raw)
In-Reply-To: <20210411095538.34129-4-mirucam@gmail.com>
On 11/04/2021 11:55, Miriam Rubio wrote:
> From: Tanushree Tumane <tanushreetumane@gmail.com>
>
> Reimplement the `bisect_run()` shell function
> in C and also add `--bisect-run` subcommand to
> `git bisect--helper` to call it from git-bisect.sh.
>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
> Signed-off-by: Miriam Rubio <mirucam@gmail.com>
> ---
> builtin/bisect--helper.c | 83 ++++++++++++++++++++++++++++++++++++++++
> git-bisect.sh | 62 +-----------------------------
> 2 files changed, 84 insertions(+), 61 deletions(-)
>
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 71963979b1..dc87fc7dd0 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -18,6 +18,7 @@ static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
> static GIT_PATH_FUNC(git_path_head_name, "head-name")
> static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
> static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
> +static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
>
> static const char * const git_bisect_helper_usage[] = {
> N_("git bisect--helper --bisect-reset [<commit>]"),
> @@ -31,6 +32,7 @@ static const char * const git_bisect_helper_usage[] = {
> N_("git bisect--helper --bisect-replay <filename>"),
> N_("git bisect--helper --bisect-skip [(<rev>|<range>)...]"),
> N_("git bisect--helper --bisect-visualize"),
> + N_("git bisect--helper --bisect-run <cmd>..."),
> NULL
> };
>
> @@ -1073,6 +1075,78 @@ static int bisect_visualize(struct bisect_terms *terms, const char **argv, int a
> return res;
> }
>
> +static int bisect_run(struct bisect_terms *terms, const char **argv, int argc)
> +{
> + int res = BISECT_OK;
> + struct strbuf command = STRBUF_INIT;
> + struct strvec args = STRVEC_INIT;
> + struct strvec run_args = STRVEC_INIT;
> + int exit = 0;
> + int temporary_stdout_fd, saved_stdout;
> +
> + if (bisect_next_check(terms, NULL))
> + return BISECT_FAILED;
> +
> + if (argc)
> + sq_quote_argv(&command, argv);
> + else
> + return BISECT_FAILED;
> +
> + run_args.v[0] = xstrdup(command.buf);
> + run_args.nr = 1;
AFAIUI manipulating the strvec directly like this means that we will
violate the promise that strvec.v is always NULL-terminated. It's
probably safer to call 'strvec_push(run_args, command.buf)' instead of
manipulating v and nr?
Violating the NULL-termination promise a problem because... (continued
below)
> +
> + while (1) {
> + strvec_clear(&args);
> + exit = 1;
> +
> + printf(_("running %s"), command.buf);
> + res = run_command_v_opt(run_args.v, RUN_USING_SHELL);
run_command_v_opt() implicitly expects a NULL-terminated list of
strings. It's not documented in run_command_v_opt()'s comments, however
run_command_v_opt() does explain that it's a wrapper around
start_command(), which uses child_process, and child_process.argv is
documented to require a NULL-terminated list.
If argv is not NULL-terminated, we hit a buffer overflow read in
prepare_shell_cmd(), which can be reproduced by running something like:
make CC=clang-11 SANITIZE=address COPTS="-Og -g" GIT_TEST_OPTS=-v
T=t6030-bisect-porcelain.sh test
which results in ASAN reporting this error:
==2116==ERROR: AddressSanitizer: global-buffer-overflow on address
0x000001a51e28 at pc 0x0000009c6c1f bp 0x7ffcf0f60670 sp 0x7ffcf0f60668
READ of size 8 at 0x000001a51e28 thread T0
#0 0x9c6c1e in prepare_shell_cmd run-command.c:284:8
#1 0x9c6c1e in prepare_cmd run-command.c:419:3
#2 0x9c6c1e in start_command run-command.c:753:6
#3 0x9c7d35 in run_command run-command.c:1015:9
#4 0x9c800c in run_command_v_opt_cd_env_tr2 run-command.c:1051:9
#5 0x9c800c in run_command_v_opt_cd_env run-command.c:1033:9
#6 0x9c800c in run_command_v_opt run-command.c:1023:9
#7 0x4e5b60 in bisect_run builtin/bisect--helper.c:1102:9
#8 0x4e5b60 in cmd_bisect__helper builtin/bisect--helper.c:1252:9
#9 0x4ce8fe in run_builtin git.c:461:11
#10 0x4ccbc8 in handle_builtin git.c:718:3
#11 0x4cb0cc in run_argv git.c:785:4
#12 0x4cb0cc in cmd_main git.c:916:19
#13 0x6beded in main common-main.c:52:11
#14 0x7f28636f7349 in __libc_start_main (/lib64/libc.so.6+0x24349)
#15 0x420769 in _start ../sysdeps/x86_64/start.S:120
0x000001a51e28 is located 56 bytes to the left of global variable
'config_update_recurse_submodules' defined in 'submodule.c:26:12'
(0x1a51e60) of size 4
0x000001a51e28 is located 0 bytes to the right of global variable
'empty_strvec' defined in 'strvec.c:5:13' (0x1a51e20) of size 8
SUMMARY: AddressSanitizer: global-buffer-overflow run-command.c:284:8 in
prepare_shell_cmd
[... snip the rest ...]
next prev parent reply other threads:[~2021-05-04 17:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-11 9:55 [PATCH v3 0/4] Finish converting git bisect to C part 4 Miriam Rubio
2021-04-11 9:55 ` [PATCH v3 1/4] run-command: make `exists_in_PATH()` non-static Miriam Rubio
2021-04-11 9:55 ` [PATCH v3 2/4] bisect--helper: reimplement `bisect_visualize()`shell function in C Miriam Rubio
2021-04-11 20:22 ` Junio C Hamano
2021-04-11 9:55 ` [PATCH v3 3/4] bisect--helper: reimplement `bisect_run` shell " Miriam Rubio
2021-04-11 20:31 ` Junio C Hamano
2021-04-11 20:33 ` Junio C Hamano
2021-05-05 9:04 ` Christian Couder
2021-05-04 17:26 ` Andrzej Hunt [this message]
2021-05-05 2:04 ` Junio C Hamano
2021-04-11 9:55 ` [PATCH v3 4/4] bisect--helper: retire `--bisect-next-check` subcommand Miriam Rubio
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3771bfc2-e4a4-3c5d-bcf5-673b403358ca@ahunt.org \
--to=andrzej@ahunt.org \
--cc=chriscool@tuxfamily.org \
--cc=git@vger.kernel.org \
--cc=mirucam@gmail.com \
--cc=tanushreetumane@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).