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run-command: prepare child environment before forking 

In order to avoid allocation between 'fork()' and 'exec()' prepare the
environment to be used in the child process prior to forking.

Switch to using 'execve()' so that the construct child environment can
used in the exec'd process.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Brandon Williams 2017-04-19 16:13:22 -07:00 committed by Junio C Hamano
parent 3a30033327
commit ae25394b4c
1 changed files with 56 additions and 10 deletions
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66
run-command.c
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@ -267,6 +267,55 @@ static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
}
}
}
static char **prep_childenv(const char *const *deltaenv)
{
extern char **environ;
char **childenv;
struct string_list env = STRING_LIST_INIT_DUP;
struct strbuf key = STRBUF_INIT;
const char *const *p;
int i;
/* Construct a sorted string list consisting of the current environ */
for (p = (const char *const *) environ; p && *p; p++) {
const char *equals = strchr(*p, '=');
if (equals) {
strbuf_reset(&key);
strbuf_add(&key, *p, equals - *p);
string_list_append(&env, key.buf)->util = (void *) *p;
} else {
string_list_append(&env, *p)->util = (void *) *p;
}
}
string_list_sort(&env);
/* Merge in 'deltaenv' with the current environ */
for (p = deltaenv; p && *p; p++) {
const char *equals = strchr(*p, '=');
if (equals) {
/* ('key=value'), insert or replace entry */
strbuf_reset(&key);
strbuf_add(&key, *p, equals - *p);
string_list_insert(&env, key.buf)->util = (void *) *p;
} else {
/* otherwise ('key') remove existing entry */
string_list_remove(&env, *p, 0);
}
}
/* Create an array of 'char *' to be used as the childenv */
childenv = xmalloc((env.nr + 1) * sizeof(char *));
for (i = 0; i < env.nr; i++)
childenv[i] = env.items[i].util;
childenv[env.nr] = NULL;
string_list_clear(&env, 0);
strbuf_release(&key);
return childenv;
}
#endif
static inline void set_cloexec(int fd)
@ -395,12 +444,14 @@ int start_command(struct child_process *cmd)
#ifndef GIT_WINDOWS_NATIVE
{
int notify_pipe[2];
char **childenv;
struct argv_array argv = ARGV_ARRAY_INIT;
if (pipe(notify_pipe))
notify_pipe[0] = notify_pipe[1] = -1;
prepare_cmd(&argv, cmd);
childenv = prep_childenv(cmd->env);
cmd->pid = fork();
failed_errno = errno;
@ -456,14 +507,6 @@ int start_command(struct child_process *cmd)
if (cmd->dir && chdir(cmd->dir))
die_errno("exec '%s': cd to '%s' failed", cmd->argv[0],
cmd->dir);
if (cmd->env) {
for (; *cmd->env; cmd->env++) {
if (strchr(*cmd->env, '='))
putenv((char *)*cmd->env);
else
unsetenv(*cmd->env);
}
}
/*
* Attempt to exec using the command and arguments starting at
@ -471,9 +514,11 @@ int start_command(struct child_process *cmd)
* 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);
execve(argv.argv[1], (char *const *) argv.argv + 1,
(char *const *) childenv);
if (errno == ENOEXEC)
execv(argv.argv[0], (char *const *) argv.argv);
execve(argv.argv[0], (char *const *) argv.argv,
(char *const *) childenv);
if (errno == ENOENT) {
if (!cmd->silent_exec_failure)
@ -509,6 +554,7 @@ int start_command(struct child_process *cmd)
close(notify_pipe[0]);
argv_array_clear(&argv);
free(childenv);
}
#else
{