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process-util: add helper to verify a pid via its pidfd

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This commit is contained in:
Luca Boccassi
2023-01-20 12:13:22 +00:00
parent a98d69f0af
commit f840c7d58d
3 changed files with 25 additions and 11 deletions
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14
src/basic/process-util.c
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@@ -1456,6 +1456,20 @@ int pidfd_get_pid(int fd, pid_t *ret) {
return parse_pid(p, ret);
}
int pidfd_verify_pid(int pidfd, pid_t pid) {
pid_t current_pid;
int r;
assert(pidfd >= 0);
assert(pid > 0);
r = pidfd_get_pid(pidfd, &current_pid);
if (r < 0)
return r;
return current_pid != pid ? -ESRCH : 0;
}
static int rlimit_to_nice(rlim_t limit) {
if (limit <= 1)
return PRIO_MAX-1; /* i.e. 19 */

1
src/basic/process-util.h
View File

@@ -190,6 +190,7 @@ assert_cc(TASKS_MAX <= (unsigned long) PID_T_MAX);
})
int pidfd_get_pid(int fd, pid_t *ret);
int pidfd_verify_pid(int pidfd, pid_t pid);
int setpriority_closest(int priority);

21
src/core/dbus-manager.c
View File

@@ -658,7 +658,7 @@ static int method_get_unit_by_pidfd(sd_bus_message *message, void *userdata, sd_
Manager *m = ASSERT_PTR(userdata);
_cleanup_free_ char *path = NULL;
int r, pidfd;
pid_t pid_early, pid_late;
pid_t pid;
Unit *u;
assert(message);
@@ -667,13 +667,13 @@ static int method_get_unit_by_pidfd(sd_bus_message *message, void *userdata, sd_
if (r < 0)
return r;
r = pidfd_get_pid(pidfd, &pid_early);
r = pidfd_get_pid(pidfd, &pid);
if (r < 0)
return sd_bus_error_set_errnof(error, r, "Failed to get PID from PIDFD: %m");
u = manager_get_unit_by_pid(m, pid_early);
u = manager_get_unit_by_pid(m, pid);
if (!u)
return sd_bus_error_setf(error, BUS_ERROR_NO_UNIT_FOR_PID, "PID "PID_FMT" does not belong to any loaded unit.", pid_early);
return sd_bus_error_setf(error, BUS_ERROR_NO_UNIT_FOR_PID, "PID "PID_FMT" does not belong to any loaded unit.", pid);
r = mac_selinux_unit_access_check(u, message, "status", error);
if (r < 0)
@@ -697,15 +697,14 @@ static int method_get_unit_by_pidfd(sd_bus_message *message, void *userdata, sd_
/* Double-check that the process is still alive and that the PID did not change before returning the
* answer. */
r = pidfd_get_pid(pidfd, &pid_late);
if (r < 0)
return sd_bus_error_set_errnof(error, r, "Failed to get PID from PIDFD: %m");
if (pid_early != pid_late)
r = pidfd_verify_pid(pidfd, pid);
if (r == -ESRCH)
return sd_bus_error_setf(error,
BUS_ERROR_NO_SUCH_PROCESS,
"The PIDFD's PID "PID_FMT" changed to "PID_FMT" during the lookup operation.",
pid_early,
pid_late);
"The PIDFD's PID "PID_FMT" changed during the lookup operation.",
pid);
if (r < 0)
return sd_bus_error_set_errnof(error, r, "Failed to get PID from PIDFD: %m");
return sd_bus_send(NULL, reply, NULL);
}