From: Andrzej Hunt Date: Tue, 04 May 2021 17:26:01 GMT Subject: Re: [PATCH v3 3/4] bisect--helper: reimplement `bisect_run` shell function in C Message-ID: <3771bfc2-e4a4-3c5d-bcf5-673b403358ca@ahunt.org> In-Reply-To: <20210411095538.34129-4-mirucam@gmail.com> On 11/04/2021 11:55, Miriam Rubio wrote: > From: Tanushree Tumane > > 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 > Signed-off-by: Tanushree Tumane > Signed-off-by: Miriam Rubio > --- > 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 []"), > @@ -31,6 +32,7 @@ static const char * const git_bisect_helper_usage[] = { > N_("git bisect--helper --bisect-replay "), > N_("git bisect--helper --bisect-skip [(|)...]"), > N_("git bisect--helper --bisect-visualize"), > + N_("git bisect--helper --bisect-run ..."), > 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 ...]