binder: Split flat_binder_object

flat_binder_object is used for both handling
binder objects and file descriptors, even though
the two are mostly independent. Since we'll
have more fixup objects in binder in the future,
instead of extending flat_binder_object again,
split out file descriptors to their own object
while retaining backwards compatibility to
existing user-space clients. All binder objects
just share a header.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Martijn Coenen <maco@google.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Amit Pundir <amit.pundir@linaro.org>
Cc: Serban Constantinescu <serban.constantinescu@arm.com>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Martijn Coenen <maco@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -145,6 +145,11 @@ module_param_call(stop_on_user_error, binder_set_stop_on_user_error,
 			binder_stop_on_user_error = 2; \
 	} while (0)
 
+#define to_flat_binder_object(hdr) \
+	container_of(hdr, struct flat_binder_object, hdr)
+
+#define to_binder_fd_object(hdr) container_of(hdr, struct binder_fd_object, hdr)
+
 enum binder_stat_types {
 	BINDER_STAT_PROC,
 	BINDER_STAT_THREAD,
@@ -1240,6 +1245,47 @@ static void binder_send_failed_reply(struct binder_transaction *t,
 	}
 }
 
+/**
+ * binder_validate_object() - checks for a valid metadata object in a buffer.
+ * @buffer:	binder_buffer that we're parsing.
+ * @offset:	offset in the buffer at which to validate an object.
+ *
+ * Return:	If there's a valid metadata object at @offset in @buffer, the
+ *		size of that object. Otherwise, it returns zero.
+ */
+static size_t binder_validate_object(struct binder_buffer *buffer, u64 offset)
+{
+	/* Check if we can read a header first */
+	struct binder_object_header *hdr;
+	size_t object_size = 0;
+
+	if (offset > buffer->data_size - sizeof(*hdr) ||
+	    buffer->data_size < sizeof(*hdr) ||
+	    !IS_ALIGNED(offset, sizeof(u32)))
+		return 0;
+
+	/* Ok, now see if we can read a complete object. */
+	hdr = (struct binder_object_header *)(buffer->data + offset);
+	switch (hdr->type) {
+	case BINDER_TYPE_BINDER:
+	case BINDER_TYPE_WEAK_BINDER:
+	case BINDER_TYPE_HANDLE:
+	case BINDER_TYPE_WEAK_HANDLE:
+		object_size = sizeof(struct flat_binder_object);
+		break;
+	case BINDER_TYPE_FD:
+		object_size = sizeof(struct binder_fd_object);
+		break;
+	default:
+		return 0;
+	}
+	if (offset <= buffer->data_size - object_size &&
+	    buffer->data_size >= object_size)
+		return object_size;
+	else
+		return 0;
+}
+
 static void binder_transaction_buffer_release(struct binder_proc *proc,
 					      struct binder_buffer *buffer,
 					      binder_size_t *failed_at)
@@ -1262,21 +1308,23 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
 	else
 		off_end = (void *)offp + buffer->offsets_size;
 	for (; offp < off_end; offp++) {
-		struct flat_binder_object *fp;
+		struct binder_object_header *hdr;
+		size_t object_size = binder_validate_object(buffer, *offp);
 
-		if (*offp > buffer->data_size - sizeof(*fp) ||
-		    buffer->data_size < sizeof(*fp) ||
-		    !IS_ALIGNED(*offp, sizeof(u32))) {
-			pr_err("transaction release %d bad offset %lld, size %zd\n",
+		if (object_size == 0) {
+			pr_err("transaction release %d bad object at offset %lld, size %zd\n",
 			       debug_id, (u64)*offp, buffer->data_size);
 			continue;
 		}
-		fp = (struct flat_binder_object *)(buffer->data + *offp);
-		switch (fp->type) {
+		hdr = (struct binder_object_header *)(buffer->data + *offp);
+		switch (hdr->type) {
 		case BINDER_TYPE_BINDER:
 		case BINDER_TYPE_WEAK_BINDER: {
-			struct binder_node *node = binder_get_node(proc, fp->binder);
+			struct flat_binder_object *fp;
+			struct binder_node *node;
 
+			fp = to_flat_binder_object(hdr);
+			node = binder_get_node(proc, fp->binder);
 			if (node == NULL) {
 				pr_err("transaction release %d bad node %016llx\n",
 				       debug_id, (u64)fp->binder);
@@ -1285,15 +1333,17 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
 			binder_debug(BINDER_DEBUG_TRANSACTION,
 				     "        node %d u%016llx\n",
 				     node->debug_id, (u64)node->ptr);
-			binder_dec_node(node, fp->type == BINDER_TYPE_BINDER, 0);
+			binder_dec_node(node, hdr->type == BINDER_TYPE_BINDER,
+					0);
 		} break;
 		case BINDER_TYPE_HANDLE:
 		case BINDER_TYPE_WEAK_HANDLE: {
+			struct flat_binder_object *fp;
 			struct binder_ref *ref;
 
+			fp = to_flat_binder_object(hdr);
 			ref = binder_get_ref(proc, fp->handle,
-					     fp->type == BINDER_TYPE_HANDLE);
-
+					     hdr->type == BINDER_TYPE_HANDLE);
 			if (ref == NULL) {
 				pr_err("transaction release %d bad handle %d\n",
 				 debug_id, fp->handle);
@@ -1302,19 +1352,21 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
 			binder_debug(BINDER_DEBUG_TRANSACTION,
 				     "        ref %d desc %d (node %d)\n",
 				     ref->debug_id, ref->desc, ref->node->debug_id);
-			binder_dec_ref(ref, fp->type == BINDER_TYPE_HANDLE);
+			binder_dec_ref(ref, hdr->type == BINDER_TYPE_HANDLE);
 		} break;
 
-		case BINDER_TYPE_FD:
+		case BINDER_TYPE_FD: {
+			struct binder_fd_object *fp = to_binder_fd_object(hdr);
+
 			binder_debug(BINDER_DEBUG_TRANSACTION,
-				     "        fd %d\n", fp->handle);
+				     "        fd %d\n", fp->fd);
 			if (failed_at)
-				task_close_fd(proc, fp->handle);
-			break;
+				task_close_fd(proc, fp->fd);
+		} break;
 
 		default:
 			pr_err("transaction release %d bad object type %x\n",
-				debug_id, fp->type);
+				debug_id, hdr->type);
 			break;
 		}
 	}
@@ -1531,28 +1583,29 @@ static void binder_transaction(struct binder_proc *proc,
 	off_end = (void *)offp + tr->offsets_size;
 	off_min = 0;
 	for (; offp < off_end; offp++) {
-		struct flat_binder_object *fp;
+		struct binder_object_header *hdr;
+		size_t object_size = binder_validate_object(t->buffer, *offp);
 
-		if (*offp > t->buffer->data_size - sizeof(*fp) ||
-		    *offp < off_min ||
-		    t->buffer->data_size < sizeof(*fp) ||
-		    !IS_ALIGNED(*offp, sizeof(u32))) {
-			binder_user_error("%d:%d got transaction with invalid offset, %lld (min %lld, max %lld)\n",
+		if (object_size == 0 || *offp < off_min) {
+			binder_user_error("%d:%d got transaction with invalid offset (%lld, min %lld max %lld) or object.\n",
 					  proc->pid, thread->pid, (u64)*offp,
 					  (u64)off_min,
-					  (u64)(t->buffer->data_size -
-					  sizeof(*fp)));
+					  (u64)t->buffer->data_size);
 			return_error = BR_FAILED_REPLY;
 			goto err_bad_offset;
 		}
-		fp = (struct flat_binder_object *)(t->buffer->data + *offp);
-		off_min = *offp + sizeof(struct flat_binder_object);
-		switch (fp->type) {
+
+		hdr = (struct binder_object_header *)(t->buffer->data + *offp);
+		off_min = *offp + object_size;
+		switch (hdr->type) {
 		case BINDER_TYPE_BINDER:
 		case BINDER_TYPE_WEAK_BINDER: {
+			struct flat_binder_object *fp;
+			struct binder_node *node;
 			struct binder_ref *ref;
-			struct binder_node *node = binder_get_node(proc, fp->binder);
 
+			fp = to_flat_binder_object(hdr);
+			node = binder_get_node(proc, fp->binder);
 			if (node == NULL) {
 				node = binder_new_node(proc, fp->binder, fp->cookie);
 				if (node == NULL) {
@@ -1580,14 +1633,14 @@ static void binder_transaction(struct binder_proc *proc,
 				return_error = BR_FAILED_REPLY;
 				goto err_binder_get_ref_for_node_failed;
 			}
-			if (fp->type == BINDER_TYPE_BINDER)
-				fp->type = BINDER_TYPE_HANDLE;
+			if (hdr->type == BINDER_TYPE_BINDER)
+				hdr->type = BINDER_TYPE_HANDLE;
 			else
-				fp->type = BINDER_TYPE_WEAK_HANDLE;
+				hdr->type = BINDER_TYPE_WEAK_HANDLE;
 			fp->binder = 0;
 			fp->handle = ref->desc;
 			fp->cookie = 0;
-			binder_inc_ref(ref, fp->type == BINDER_TYPE_HANDLE,
+			binder_inc_ref(ref, hdr->type == BINDER_TYPE_HANDLE,
 				       &thread->todo);
 
 			trace_binder_transaction_node_to_ref(t, node, ref);
@@ -1598,11 +1651,12 @@ static void binder_transaction(struct binder_proc *proc,
 		} break;
 		case BINDER_TYPE_HANDLE:
 		case BINDER_TYPE_WEAK_HANDLE: {
+			struct flat_binder_object *fp;
 			struct binder_ref *ref;
 
+			fp = to_flat_binder_object(hdr);
 			ref = binder_get_ref(proc, fp->handle,
-					     fp->type == BINDER_TYPE_HANDLE);
-
+					     hdr->type == BINDER_TYPE_HANDLE);
 			if (ref == NULL) {
 				binder_user_error("%d:%d got transaction with invalid handle, %d\n",
 						proc->pid,
@@ -1616,13 +1670,15 @@ static void binder_transaction(struct binder_proc *proc,
 				goto err_binder_get_ref_failed;
 			}
 			if (ref->node->proc == target_proc) {
-				if (fp->type == BINDER_TYPE_HANDLE)
-					fp->type = BINDER_TYPE_BINDER;
+				if (hdr->type == BINDER_TYPE_HANDLE)
+					hdr->type = BINDER_TYPE_BINDER;
 				else
-					fp->type = BINDER_TYPE_WEAK_BINDER;
+					hdr->type = BINDER_TYPE_WEAK_BINDER;
 				fp->binder = ref->node->ptr;
 				fp->cookie = ref->node->cookie;
-				binder_inc_node(ref->node, fp->type == BINDER_TYPE_BINDER, 0, NULL);
+				binder_inc_node(ref->node,
+						hdr->type == BINDER_TYPE_BINDER,
+						0, NULL);
 				trace_binder_transaction_ref_to_node(t, ref);
 				binder_debug(BINDER_DEBUG_TRANSACTION,
 					     "        ref %d desc %d -> node %d u%016llx\n",
@@ -1639,7 +1695,9 @@ static void binder_transaction(struct binder_proc *proc,
 				fp->binder = 0;
 				fp->handle = new_ref->desc;
 				fp->cookie = 0;
-				binder_inc_ref(new_ref, fp->type == BINDER_TYPE_HANDLE, NULL);
+				binder_inc_ref(new_ref,
+					       hdr->type == BINDER_TYPE_HANDLE,
+					       NULL);
 				trace_binder_transaction_ref_to_ref(t, ref,
 								    new_ref);
 				binder_debug(BINDER_DEBUG_TRANSACTION,
@@ -1652,25 +1710,26 @@ static void binder_transaction(struct binder_proc *proc,
 		case BINDER_TYPE_FD: {
 			int target_fd;
 			struct file *file;
+			struct binder_fd_object *fp = to_binder_fd_object(hdr);
 
 			if (reply) {
 				if (!(in_reply_to->flags & TF_ACCEPT_FDS)) {
 					binder_user_error("%d:%d got reply with fd, %d, but target does not allow fds\n",
-						proc->pid, thread->pid, fp->handle);
+						proc->pid, thread->pid, fp->fd);
 					return_error = BR_FAILED_REPLY;
 					goto err_fd_not_allowed;
 				}
 			} else if (!target_node->accept_fds) {
 				binder_user_error("%d:%d got transaction with fd, %d, but target does not allow fds\n",
-					proc->pid, thread->pid, fp->handle);
+					proc->pid, thread->pid, fp->fd);
 				return_error = BR_FAILED_REPLY;
 				goto err_fd_not_allowed;
 			}
 
-			file = fget(fp->handle);
+			file = fget(fp->fd);
 			if (file == NULL) {
 				binder_user_error("%d:%d got transaction with invalid fd, %d\n",
-					proc->pid, thread->pid, fp->handle);
+					proc->pid, thread->pid, fp->fd);
 				return_error = BR_FAILED_REPLY;
 				goto err_fget_failed;
 			}
@@ -1688,17 +1747,18 @@ static void binder_transaction(struct binder_proc *proc,
 				goto err_get_unused_fd_failed;
 			}
 			task_fd_install(target_proc, target_fd, file);
-			trace_binder_transaction_fd(t, fp->handle, target_fd);
+			trace_binder_transaction_fd(t, fp->fd, target_fd);
 			binder_debug(BINDER_DEBUG_TRANSACTION,
-				     "        fd %d -> %d\n", fp->handle, target_fd);
+				     "        fd %d -> %d\n", fp->fd,
+				     target_fd);
 			/* TODO: fput? */
-			fp->binder = 0;
-			fp->handle = target_fd;
+			fp->pad_binder = 0;
+			fp->fd = target_fd;
 		} break;
 
 		default:
 			binder_user_error("%d:%d got transaction with invalid object type, %x\n",
-				proc->pid, thread->pid, fp->type);
+				proc->pid, thread->pid, hdr->type);
 			return_error = BR_FAILED_REPLY;
 			goto err_bad_object_type;
 		}

include/uapi/linux/android/binder.h

@@ -48,6 +48,14 @@ typedef __u64 binder_size_t;
 typedef __u64 binder_uintptr_t;
 #endif
 
+/**
+ * struct binder_object_header - header shared by all binder metadata objects.
+ * @type:	type of the object
+ */
+struct binder_object_header {
+	__u32        type;
+};
+
 /*
  * This is the flattened representation of a Binder object for transfer
  * between processes.  The 'offsets' supplied as part of a binder transaction
@@ -56,9 +64,8 @@ typedef __u64 binder_uintptr_t;
  * between processes.
  */
 struct flat_binder_object {
-	/* 8 bytes for large_flat_header. */
-	__u32		type;
-	__u32		flags;
+	struct binder_object_header	hdr;
+	__u32				flags;
 
 	/* 8 bytes of data. */
 	union {
@@ -70,6 +77,24 @@ struct flat_binder_object {
 	binder_uintptr_t	cookie;
 };
 
+/**
+ * struct binder_fd_object - describes a filedescriptor to be fixed up.
+ * @hdr:	common header structure
+ * @pad_flags:	padding to remain compatible with old userspace code
+ * @pad_binder:	padding to remain compatible with old userspace code
+ * @fd:		file descriptor
+ * @cookie:	opaque data, used by user-space
+ */
+struct binder_fd_object {
+	struct binder_object_header	hdr;
+	__u32				pad_flags;
+	union {
+		binder_uintptr_t	pad_binder;
+		__u32			fd;
+	};
+
+	binder_uintptr_t		cookie;
+};
 /*
  * On 64-bit platforms where user code may run in 32-bits the driver must
  * translate the buffer (and local binder) addresses appropriately.