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core: use fexecve() to spawn children

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We base the smack/selinux setup on the executable. Let's open the file
once and use the same fd for that setup and the subsequent execve.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-09-17 15:01:26 +02:00
parent 5ca9139ace
commit b83d505087
2 changed files with 14 additions and 8 deletions
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21
src/core/execute.c
View File

@ -2881,11 +2881,11 @@ static int setup_credentials(
#if ENABLE_SMACK
static int setup_smack(
const ExecContext *context,
const char *executable) {
int executable_fd) {
int r;
assert(context);
assert(executable);
assert(executable_fd >= 0);
if (context->smack_process_label) {
r = mac_smack_apply_pid(0, context->smack_process_label);
@ -2896,7 +2896,7 @@ static int setup_smack(
else {
_cleanup_free_ char *exec_label = NULL;
r = mac_smack_read(executable, SMACK_ATTR_EXEC, &exec_label);
r = mac_smack_read_fd(executable_fd, SMACK_ATTR_EXEC, &exec_label);
if (r < 0 && !IN_SET(r, -ENODATA, -EOPNOTSUPP))
return r;
@ -3717,7 +3717,7 @@ static int exec_child(
/* In case anything used libc syslog(), close this here, too */
closelog();
int keep_fds[n_fds + 1];
int keep_fds[n_fds + 2];
memcpy_safe(keep_fds, fds, n_fds * sizeof(int));
n_keep_fds = n_fds;
@ -4230,7 +4230,8 @@ static int exec_child(
* shall execute. */
_cleanup_free_ char *executable = NULL;
r = find_executable_full(command->path, false, &executable, NULL);
_cleanup_close_ int executable_fd = -1;
r = find_executable_full(command->path, false, &executable, &executable_fd);
if (r < 0) {
if (r != -ENOMEM && (command->flags & EXEC_COMMAND_IGNORE_FAILURE)) {
log_struct_errno(LOG_INFO, r,
@ -4253,6 +4254,12 @@ static int exec_child(
"EXECUTABLE=%s", command->path);
}
r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, executable_fd, &executable_fd);
if (r < 0) {
*exit_status = EXIT_FDS;
return log_unit_error_errno(unit, r, "Failed to shift fd and set FD_CLOEXEC: %m");
}
#if HAVE_SELINUX
if (needs_sandboxing && use_selinux && params->selinux_context_net && socket_fd >= 0) {
r = mac_selinux_get_child_mls_label(socket_fd, executable, context->selinux_context, &mac_selinux_context_net);
@ -4301,7 +4308,7 @@ static int exec_child(
/* LSM Smack needs the capability CAP_MAC_ADMIN to change the current execution security context of the
* process. This is the latest place before dropping capabilities. Other MAC context are set later. */
if (use_smack) {
r = setup_smack(context, executable);
r = setup_smack(context, executable_fd);
if (r < 0) {
*exit_status = EXIT_SMACK_PROCESS_LABEL;
return log_unit_error_errno(unit, r, "Failed to set SMACK process label: %m");
@ -4571,7 +4578,7 @@ static int exec_child(
}
}
execve(executable, final_argv, accum_env);
fexecve(executable_fd, final_argv, accum_env);
r = -errno;
if (exec_fd >= 0) {

1
src/shared/exec-util.c
View File

@ -33,7 +33,6 @@
assert_cc(EAGAIN == EWOULDBLOCK);
static int do_spawn(const char *path, char *argv[], int stdout_fd, pid_t *pid) {
pid_t _pid;
int r;