Merge "cutils: return the remote uid on netlink recv failure" (b012679f) · Commits · e / os / android_system_core

include/cutils/uevent.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,7 @@ extern "C" {

		int uevent_open_socket(int buf_sz, bool passcred);
		ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length);
		ssize_t uevent_kernel_multicast_uid_recv(int socket, void buffer, size_t length, uid_t uid);

		#ifdef __cplusplus
		}

libcutils/uevent.c

+25 −6

Original line number	Diff line number	Diff line
		@@ -29,7 +29,24 @@
		/**
		* Like recv(), but checks that messages actually originate from the kernel.
		*/
		ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length) {
		ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length)
		{
		uid_t user = -1;
		return uevent_kernel_multicast_uid_recv(socket, buffer, length, &user);
		}

		/**
		* Like the above, but passes a uid_t in by reference. In the event that this
		* fails due to a bad uid check, the uid_t will be set to the uid of the
		* socket's peer.
		*
		* If this method rejects a netlink message from outside the kernel, it
		* returns -1, sets errno to EIO, and sets "user" to the UID associated with the
		* message. If the peer UID cannot be determined, "user" is set to -1."
		*/
		ssize_t uevent_kernel_multicast_uid_recv(int socket, void *buffer,
		size_t length, uid_t *user)
		{
		struct iovec iov = { buffer, length };
		struct sockaddr_nl addr;
		char control[CMSG_SPACE(sizeof(struct ucred))];
		@@ -43,16 +60,12 @@ ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length) {
		0,
		};

		*user = -1;
		ssize_t n = recvmsg(socket, &hdr, 0);
		if (n <= 0) {
		return n;
		}

		if (addr.nl_groups == 0 \|\| addr.nl_pid != 0) {
		/* ignoring non-kernel or unicast netlink message */
		goto out;
		}

		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
		if (cmsg == NULL \|\| cmsg->cmsg_type != SCM_CREDENTIALS) {
		/* ignoring netlink message with no sender credentials */
		@@ -60,11 +73,17 @@ ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length) {
		}

		struct ucred cred = (struct ucred )CMSG_DATA(cmsg);
		*user = cred->uid;
		if (cred->uid != 0) {
		/* ignoring netlink message from non-root user */
		goto out;
		}

		if (addr.nl_groups == 0 \|\| addr.nl_pid != 0) {
		/* ignoring non-kernel or unicast netlink message */
		goto out;
		}

		return n;

		out: