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From: Brandon Williams <bmwill@google.com>
To: git@vger.kernel.org
Cc: Brandon Williams <bmwill@google.com>, jrnieder@gmail.com, e@80x24.org
Subject: [PATCH v4 04/10] run-command: use the async-signal-safe execv instead of execvp
Date: Mon, 17 Apr 2017 15:08:12 -0700	[thread overview]
Message-ID: <20170417220818.44917-5-bmwill@google.com> (raw)
In-Reply-To: <20170417220818.44917-1-bmwill@google.com>

Convert the function used to exec from 'execvp()' to 'execv()' as the (p)
variant of exec isn't async-signal-safe and has the potential to call malloc
during the path resolution it performs.  Instead we simply do the path
resolution ourselves during the preparation stage prior to forking.  There also
don't exist any portable (p) variants which also take in an environment to use
in the exec'd process.  This allows easy migration to using 'execve()' in a
future patch.

Also, as noted in [1], in the event of an ENOEXEC the (p) variants of
exec will attempt to execute the command by interpreting it with the
'sh' utility.  To maintain this functionality, if 'execv()' fails with
ENOEXEC, start_command will atempt to execute the command by
interpreting it with 'sh'.

[1] http://pubs.opengroup.org/onlinepubs/009695399/functions/exec.html

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 run-command.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/run-command.c b/run-command.c
index d8d143795..1c7a3b611 100644
--- a/run-command.c
+++ b/run-command.c
@@ -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);
@@ -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;
+		}
+	}
 }
 #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);
+		if (errno == ENOEXEC)
+			execv(argv.argv[0], (char *const *) argv.argv);
 
 		if (errno == ENOENT) {
 			if (!cmd->silent_exec_failure)
-- 
2.12.2.762.g0e3151a226-goog


  parent reply	other threads:[~2017-04-17 22:08 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       ` Brandon Williams [this message]
2017-04-17 22:08       ` [PATCH v4 05/10] run-command: prepare child environment " 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
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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