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-rw-r--r--src/core/execute.c23
1 files changed, 21 insertions, 2 deletions
diff --git a/src/core/execute.c b/src/core/execute.c
index a7e2362236..7796c07fcf 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -50,6 +50,7 @@
#include <sys/apparmor.h>
#endif
+#include "barrier.h"
#include "sd-messages.h"
#include "rm-rf.h"
#include "strv.h"
@@ -768,10 +769,11 @@ static int setup_pam(
.appdata_ptr = NULL
};
+ _cleanup_(barrier_destroy) Barrier barrier = BARRIER_NULL;
pam_handle_t *handle = NULL;
sigset_t old_ss;
int pam_code = PAM_SUCCESS;
- int err;
+ int err = 0;
char **e = NULL;
bool close_session = false;
pid_t pam_pid = 0, parent_pid;
@@ -788,6 +790,10 @@ static int setup_pam(
* daemon. We do things this way to ensure that the main PID
* of the daemon is the one we initially fork()ed. */
+ err = barrier_create(&barrier);
+ if (err < 0)
+ goto fail;
+
if (log_get_max_level() < LOG_DEBUG)
flags |= PAM_SILENT;
@@ -836,6 +842,7 @@ static int setup_pam(
/* The child's job is to reset the PAM session on
* termination */
+ barrier_set_role(&barrier, BARRIER_CHILD);
/* This string must fit in 10 chars (i.e. the length
* of "/sbin/init"), to look pretty in /bin/ps */
@@ -863,6 +870,11 @@ static int setup_pam(
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
goto child_finish;
+ /* Tell the parent that our setup is done. This is especially
+ * important regarding dropping privileges. Otherwise, unit
+ * setup might race against our setresuid(2) call. */
+ barrier_place(&barrier);
+
/* Check if our parent process might already have
* died? */
if (getppid() == parent_pid) {
@@ -898,6 +910,8 @@ static int setup_pam(
_exit(r);
}
+ barrier_set_role(&barrier, BARRIER_PARENT);
+
/* If the child was forked off successfully it will do all the
* cleanups, so forget about the handle here. */
handle = NULL;
@@ -909,6 +923,11 @@ static int setup_pam(
* might have opened it, but we don't want this fd around. */
closelog();
+ /* Synchronously wait for the child to initialize. We don't care for
+ * errors as we cannot recover. However, warn loudly if it happens. */
+ if (!barrier_place_and_sync(&barrier))
+ log_error("PAM initialization failed");
+
*pam_env = e;
e = NULL;
@@ -919,7 +938,7 @@ fail:
log_error("PAM failed: %s", pam_strerror(handle, pam_code));
err = -EPERM; /* PAM errors do not map to errno */
} else {
- err = log_error_errno(errno, "PAM failed: %m");
+ err = log_error_errno(err < 0 ? err : errno, "PAM failed: %m");
}
if (handle) {