From: Junio C Hamano <gitster@pobox.com>
To: Brandon Williams <bmwill@google.com>
Cc: git@vger.kernel.org, j6t@kdbg.org, sbeller@google.com,
e@80x24.org, jrnieder@gmail.com
Subject: Re: [PATCH v6 04/11] run-command: use the async-signal-safe execv instead of execvp
Date: Wed, 17 May 2017 11:15:43 +0900 [thread overview]
Message-ID: <xmqqfug4z0s0.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20170419231327.49895-5-bmwill@google.com> (Brandon Williams's message of "Wed, 19 Apr 2017 16:13:20 -0700")
Brandon Williams <bmwill@google.com> writes:
> @@ -238,6 +238,12 @@ static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
> if (!cmd->argv[0])
> die("BUG: command is empty");
>
> + /*
> + * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
> + * attempt to interpret the command with 'sh'.
> + */
> + argv_array_push(out, SHELL_PATH);
> +
> if (cmd->git_cmd) {
> argv_array_push(out, "git");
> argv_array_pushv(out, cmd->argv);
So, given "cat-file", "-t", "HEAD" with cmd->git_cmd == TRUE, this
will now prepare ("/bin/sh", "git", "cat-file", "-t", "HEAD", NULL) in
the argv-array, and then ...
> @@ -246,6 +252,20 @@ static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
> } else {
> argv_array_pushv(out, cmd->argv);
> }
> +
> + /*
> + * If there are no '/' characters in the command then perform a path
> + * lookup and use the resolved path as the command to exec. If there
> + * are no '/' characters or if the command wasn't found in the path,
> + * have exec attempt to invoke the command directly.
> + */
> + if (!strchr(out->argv[1], '/')) {
> + char *program = locate_in_PATH(out->argv[1]);
> + if (program) {
> + free((char *)out->argv[1]);
> + out->argv[1] = program;
> + }
> + }
... turn the first element from "git" to "/usr/bin/git", i.e.
("/bin/sh", "/usr/bin/git", "cat-file", "-t", "HEAD", NULL)
which ...
> #endif
>
> @@ -445,7 +465,15 @@ int start_command(struct child_process *cmd)
> }
> }
>
> - sane_execvp(argv.argv[0], (char *const *) argv.argv);
> + /*
> + * Attempt to exec using the command and arguments starting at
> + * argv.argv[1]. argv.argv[0] contains SHELL_PATH which will
> + * be used in the event exec failed with ENOEXEC at which point
> + * we will try to interpret the command using 'sh'.
> + */
> + execv(argv.argv[1], (char *const *) argv.argv + 1);
... first is given without the leading "/bin/sh", as the end-user
intended (sort of), but if it fails
> + if (errno == ENOEXEC)
> + execv(argv.argv[0], (char *const *) argv.argv);
"/bin/sh" tries to run "/usr/bin/git" that was not executable (well,
the one in "usr/bin/" would have +x bit, but let's pretend that we
are trying to run one from bin-wrappers/ and somehow forgot +x bit)?
I think all of that is sensible, but there is one "huh?" I can't
figure out. Typically we do "sh -c git cat-file -t HEAD" but this
lacks the "-c" (cf. the original prepare_shell_cmd()); why do we not
need it in this case?
Thanks.
next prev parent reply other threads:[~2017-05-17 2:15 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-10 23:49 [PATCH 0/5] forking and threading Brandon Williams
2017-04-10 23:49 ` [PATCH 1/5] run-command: convert sane_execvp to sane_execvpe Brandon Williams
2017-04-12 19:22 ` Brandon Williams
2017-04-10 23:49 ` [PATCH 2/5] run-command: prepare argv before forking Brandon Williams
2017-04-10 23:49 ` [PATCH 3/5] run-command: allocate child_err " Brandon Williams
2017-04-10 23:49 ` [PATCH 4/5] run-command: prepare child environment " Brandon Williams
2017-04-11 0:58 ` Jonathan Nieder
2017-04-11 17:27 ` Brandon Williams
2017-04-11 17:30 ` Jonathan Nieder
2017-04-10 23:49 ` [PATCH 5/5] run-command: add note about forking and threading Brandon Williams
2017-04-11 0:26 ` Jonathan Nieder
2017-04-11 0:53 ` Eric Wong
2017-04-11 17:33 ` Jonathan Nieder
2017-04-11 17:34 ` Brandon Williams
2017-04-11 17:40 ` Eric Wong
2017-04-11 7:05 ` [PATCH 6/5] run-command: avoid potential dangers in forked child Eric Wong
2017-04-11 16:29 ` Brandon Williams
2017-04-11 16:59 ` Eric Wong
2017-04-11 17:17 ` Brandon Williams
2017-04-11 17:37 ` [PATCH 0/5] forking and threading Jonathan Nieder
2017-04-11 17:54 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 0/6] " Brandon Williams
2017-04-13 18:32 ` [PATCH v2 1/6] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-13 20:43 ` Jonathan Nieder
2017-04-13 20:59 ` Eric Wong
2017-04-13 21:35 ` Brandon Williams
2017-04-13 21:39 ` Eric Wong
2017-04-13 18:32 ` [PATCH v2 2/6] run-command: prepare command before forking Brandon Williams
2017-04-13 21:14 ` Jonathan Nieder
2017-04-13 22:41 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 3/6] run-command: prepare child environment " Brandon Williams
2017-04-13 18:32 ` [PATCH v2 4/6] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-13 19:29 ` Eric Wong
2017-04-13 19:43 ` Brandon Williams
2017-04-13 18:32 ` [PATCH v2 5/6] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-13 18:32 ` [PATCH v2 6/6] run-command: add note about forking and threading Brandon Williams
2017-04-13 20:50 ` [PATCH v2 0/6] " Jonathan Nieder
2017-04-13 23:44 ` Brandon Williams
2017-04-13 21:14 ` [PATCH 7/6] run-command: block signals between fork and execve Eric Wong
2017-04-13 23:37 ` Brandon Williams
2017-04-14 2:42 ` Brandon Williams
2017-04-14 5:26 ` Eric Wong
2017-04-14 5:35 ` Eric Wong
2017-04-14 16:58 ` [PATCH v3 00/10] forking and threading Brandon Williams
2017-04-14 16:58 ` [PATCH v3 01/10] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-14 16:58 ` [PATCH v3 02/10] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-14 16:58 ` [PATCH v3 03/10] run-command: prepare command before forking Brandon Williams
2017-04-14 16:58 ` [PATCH v3 04/10] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-14 16:58 ` [PATCH v3 05/10] run-command: prepare child environment before forking Brandon Williams
2017-04-14 16:58 ` [PATCH v3 06/10] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-14 19:38 ` Eric Wong
2017-04-14 20:19 ` Brandon Williams
2017-04-14 16:58 ` [PATCH v3 07/10] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-14 18:50 ` Eric Wong
2017-04-14 20:22 ` Brandon Williams
2017-04-14 16:59 ` [PATCH v3 08/10] run-command: handle dup2 and close errors " Brandon Williams
2017-04-14 16:59 ` [PATCH v3 09/10] run-command: add note about forking and threading Brandon Williams
2017-04-14 16:59 ` [PATCH v3 10/10] run-command: block signals between fork and execve Brandon Williams
2017-04-14 20:24 ` Brandon Williams
2017-04-14 21:35 ` Eric Wong
2017-04-17 22:08 ` [PATCH v4 00/10] forking and threading Brandon Williams
2017-04-17 22:08 ` [PATCH v4 01/10] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-17 22:08 ` [PATCH v4 02/10] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-17 22:08 ` [PATCH v4 03/10] run-command: prepare command before forking Brandon Williams
2017-04-17 22:08 ` [PATCH v4 04/10] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-17 22:08 ` [PATCH v4 05/10] run-command: prepare child environment before forking Brandon Williams
2017-04-18 0:26 ` Eric Wong
2017-04-18 21:02 ` Brandon Williams
2017-04-17 22:08 ` [PATCH v4 06/10] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-17 22:08 ` [PATCH v4 07/10] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-17 22:08 ` [PATCH v4 08/10] run-command: handle dup2 and close errors " Brandon Williams
2017-04-17 22:08 ` [PATCH v4 09/10] run-command: add note about forking and threading Brandon Williams
2017-04-17 22:08 ` [PATCH v4 10/10] run-command: block signals between fork and execve Brandon Williams
2017-04-18 23:17 ` [PATCH v5 00/11] forking and threading Brandon Williams
2017-04-18 23:17 ` [PATCH v5 01/11] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-18 23:17 ` [PATCH v5 02/11] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-19 5:43 ` Johannes Sixt
2017-04-19 6:21 ` Johannes Sixt
2017-04-19 15:56 ` Brandon Williams
2017-04-19 18:18 ` Johannes Sixt
2017-04-20 10:47 ` Johannes Schindelin
2017-04-20 17:02 ` Brandon Williams
2017-04-20 20:24 ` Johannes Schindelin
2017-04-20 20:49 ` Brandon Williams
2017-04-18 23:17 ` [PATCH v5 03/11] run-command: prepare command before forking Brandon Williams
2017-04-18 23:17 ` [PATCH v5 04/11] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-04-18 23:17 ` [PATCH v5 05/11] string-list: add string_list_remove function Brandon Williams
2017-04-18 23:31 ` Stefan Beller
2017-04-18 23:36 ` Brandon Williams
2017-04-18 23:40 ` Stefan Beller
2017-04-18 23:18 ` [PATCH v5 06/11] run-command: prepare child environment before forking Brandon Williams
2017-04-18 23:18 ` [PATCH v5 07/11] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-18 23:18 ` [PATCH v5 08/11] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-18 23:18 ` [PATCH v5 09/11] run-command: handle dup2 and close errors " Brandon Williams
2017-04-18 23:18 ` [PATCH v5 10/11] run-command: add note about forking and threading Brandon Williams
2017-04-18 23:18 ` [PATCH v5 11/11] run-command: block signals between fork and execve Brandon Williams
2017-04-19 6:00 ` Johannes Sixt
2017-04-19 7:48 ` Eric Wong
2017-04-19 16:10 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 00/11] forking and threading Brandon Williams
2017-04-19 23:13 ` [PATCH v6 01/11] t5550: use write_script to generate post-update hook Brandon Williams
2017-04-19 23:13 ` [PATCH v6 02/11] t0061: run_command executes scripts without a #! line Brandon Williams
2017-04-20 10:49 ` Johannes Schindelin
2017-04-20 16:58 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 03/11] run-command: prepare command before forking Brandon Williams
2017-04-19 23:13 ` [PATCH v6 04/11] run-command: use the async-signal-safe execv instead of execvp Brandon Williams
2017-05-17 2:15 ` Junio C Hamano [this message]
2017-05-17 2:26 ` Jeff King
2017-05-17 2:28 ` Jeff King
2017-05-17 3:41 ` Junio C Hamano
2017-05-17 14:52 ` Brandon Williams
2017-04-19 23:13 ` [PATCH v6 05/11] string-list: add string_list_remove function Brandon Williams
2017-04-19 23:13 ` [PATCH v6 06/11] run-command: prepare child environment before forking Brandon Williams
2017-04-19 23:13 ` [PATCH v6 07/11] run-command: don't die in child when duping /dev/null Brandon Williams
2017-04-19 23:13 ` [PATCH v6 08/11] run-command: eliminate calls to error handling functions in child Brandon Williams
2017-04-19 23:13 ` [PATCH v6 09/11] run-command: handle dup2 and close errors " Brandon Williams
2017-04-19 23:13 ` [PATCH v6 10/11] run-command: add note about forking and threading Brandon Williams
2017-04-19 23:13 ` [PATCH v6 11/11] run-command: block signals between fork and execve Brandon Williams
2017-04-24 22:37 ` [PATCH v6 00/11] forking and threading Brandon Williams
2017-04-24 23:50 ` [PATCH v6 12/11] run-command: don't try to execute directories Brandon Williams
2017-04-25 0:17 ` Jonathan Nieder
2017-04-25 1:58 ` Junio C Hamano
2017-04-25 2:51 ` Jonathan Nieder
2017-04-25 2:56 ` Jeff King
2017-04-25 1:47 ` Junio C Hamano
2017-04-25 2:57 ` Jonathan Nieder
2017-04-25 17:54 ` [PATCH v7 1/2] exec_cmd: expose is_executable function Brandon Williams
2017-04-25 17:54 ` [PATCH v7 2/2] run-command: don't try to execute directories Brandon Williams
2017-04-25 18:51 ` Jonathan Nieder
2017-04-25 19:32 ` Brandon Williams
2017-04-25 18:04 ` [PATCH v7 1/2] exec_cmd: expose is_executable function Jonathan Nieder
2017-04-25 18:18 ` Johannes Sixt
2017-04-25 18:38 ` Brandon Williams
2017-04-25 23:46 ` [PATCH v8 1/2] run-command: " Brandon Williams
2017-04-25 23:47 ` [PATCH v8 2/2] run-command: restrict PATH search to executable files Brandon Williams
2017-04-25 23:50 ` Jonathan Nieder
2017-04-26 1:44 ` Junio C Hamano
2017-04-26 17:10 ` [PATCH v9 " Brandon Williams
2017-04-27 0:33 ` Junio C Hamano
2017-04-25 23:48 ` [PATCH v8 1/2] run-command: expose is_executable function Jonathan Nieder
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