Zygote : Block SIGCHLD during fork. (35b84533) · Commits · e / os / android_frameworks_base

core/jni/com_android_internal_os_Zygote.cpp

+25 −0

Original line number	Diff line number	Diff line
		@@ -446,6 +446,20 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		ckTime(start, "ForkAndSpecializeCommon:SetSigChldHandler");


		sigset_t sigchld;
		sigemptyset(&sigchld);
		sigaddset(&sigchld, SIGCHLD);

		// Temporarily block SIGCHLD during forks. The SIGCHLD handler might
		// log, which would result in the logging FDs we close being reopened.
		// This would cause failures because the FDs are not whitelisted.
		//
		// Note that the zygote process is single threaded at this point.
		if (sigprocmask(SIG_BLOCK, &sigchld, NULL) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_BLOCK, { SIGCHLD }) failed.");
		}

		// Close any logging related FDs before we start evaluating the list of
		// file descriptors.
		__android_log_close();
		@@ -479,6 +493,11 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		RuntimeAbort(env, __LINE__, "Unable to reopen whitelisted descriptors.");
		}

		if (sigprocmask(SIG_UNBLOCK, &sigchld, NULL) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed.");
		}

		// Keep capabilities across UID change, unless we're staying root.
		if (uid != 0) {
		EnableKeepCapabilities(env);
		@@ -613,6 +632,12 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		}
		} else if (pid > 0) {
		// the parent process

		// We blocked SIGCHLD prior to a fork, we unblock it here.
		if (sigprocmask(SIG_UNBLOCK, &sigchld, NULL) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed.");
		}
		}
		return pid;
		}