android: binder: Move buffer out of area shared with user space

Binder driver allocates buffer meta data in a region that is mapped
in user space. These meta data contain pointers in the kernel.

This patch allocates buffer meta data on the kernel heap that is
not mapped in user space, and uses a pointer to refer to the data mapped.

Also move alloc->buffers initialization from mmap to init since it's
now used even when mmap failed or was not called.

Bug: 36007193
Change-Id: Id5136048bdb7b796f59de066de7ea7df410498f5
Signed-off-by: Sherry Yang <sherryy@android.com>

1 files changed, 86 insertions, 54 deletions

diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index 93877455b94a..729b02458506 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -308,7 +308,7 @@ struct binder_buffer {
 	size_t data_size;
 	size_t offsets_size;
 	size_t extra_buffers_size;
-	uint8_t data[0];
+	void *data;
 };
 
 enum binder_deferred_state {
@@ -557,8 +557,9 @@ static size_t binder_buffer_size(struct binder_proc *proc,
 				 struct binder_buffer *buffer)
 {
 	if (list_is_last(&buffer->entry, &proc->buffers))
-		return proc->buffer + proc->buffer_size - (void *)buffer->data;
-	return (size_t)binder_buffer_next(buffer) - (size_t)buffer->data;
+		return (u8 *)proc->buffer +
+			proc->buffer_size - (u8 *)buffer->data;
+	return (u8 *)binder_buffer_next(buffer)->data - (u8 *)buffer->data;
 }
 
 static void binder_insert_free_buffer(struct binder_proc *proc,
@@ -608,9 +609,9 @@ static void binder_insert_allocated_buffer(struct binder_proc *proc,
 		buffer = rb_entry(parent, struct binder_buffer, rb_node);
 		BUG_ON(buffer->free);
 
-		if (new_buffer < buffer)
+		if (new_buffer->data < buffer->data)
 			p = &parent->rb_left;
-		else if (new_buffer > buffer)
+		else if (new_buffer->data > buffer->data)
 			p = &parent->rb_right;
 		else
 			BUG();
@@ -624,18 +625,17 @@ static struct binder_buffer *binder_buffer_lookup(struct binder_proc *proc,
 {
 	struct rb_node *n = proc->allocated_buffers.rb_node;
 	struct binder_buffer *buffer;
-	struct binder_buffer *kern_ptr;
+	void *kern_ptr;
 
-	kern_ptr = (struct binder_buffer *)(user_ptr - proc->user_buffer_offset
-		- offsetof(struct binder_buffer, data));
+	kern_ptr = (void *)(user_ptr - proc->user_buffer_offset);
 
 	while (n) {
 		buffer = rb_entry(n, struct binder_buffer, rb_node);
 		BUG_ON(buffer->free);
 
-		if (kern_ptr < buffer)
+		if (kern_ptr < buffer->data)
 			n = n->rb_left;
-		else if (kern_ptr > buffer)
+		else if (kern_ptr > buffer->data)
 			n = n->rb_right;
 		else
 			return buffer;
@@ -809,6 +809,9 @@ static struct binder_buffer *binder_alloc_buf(struct binder_proc *proc,
 		return NULL;
 	}
 
+	/* Pad 0-size buffers so they get assigned unique addresses */
+	size = max(size, sizeof(void *));
+
 	while (n) {
 		buffer = rb_entry(n, struct binder_buffer, rb_node);
 		BUG_ON(!buffer->free);
@@ -840,30 +843,32 @@ static struct binder_buffer *binder_alloc_buf(struct binder_proc *proc,
 
 	has_page_addr =
 		(void *)(((uintptr_t)buffer->data + buffer_size) & PAGE_MASK);
-	if (n == NULL) {
-		if (size + sizeof(struct binder_buffer) + 4 >= buffer_size)
-			buffer_size = size; /* no room for other buffers */
-		else
-			buffer_size = size + sizeof(struct binder_buffer);
-	}
+	WARN_ON(n && buffer_size != size);
 	end_page_addr =
-		(void *)PAGE_ALIGN((uintptr_t)buffer->data + buffer_size);
+		(void *)PAGE_ALIGN((uintptr_t)buffer->data + size);
 	if (end_page_addr > has_page_addr)
 		end_page_addr = has_page_addr;
 	if (binder_update_page_range(proc, 1,
 	    (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr, NULL))
 		return NULL;
-
-	rb_erase(best_fit, &proc->free_buffers);
-	buffer->free = 0;
-	binder_insert_allocated_buffer(proc, buffer);
 	if (buffer_size != size) {
-		struct binder_buffer *new_buffer = (void *)buffer->data + size;
+		struct binder_buffer *new_buffer;
 
+		new_buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+		if (!new_buffer) {
+			pr_err("%s: %d failed to alloc new buffer struct\n",
+			       __func__, proc->pid);
+			goto err_alloc_buf_struct_failed;
+		}
+		new_buffer->data = (u8 *)buffer->data + size;
 		list_add(&new_buffer->entry, &buffer->entry);
 		new_buffer->free = 1;
 		binder_insert_free_buffer(proc, new_buffer);
 	}
+
+	rb_erase(best_fit, &proc->free_buffers);
+	buffer->free = 0;
+	binder_insert_allocated_buffer(proc, buffer);
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
 		     "%d: binder_alloc_buf size %zd got %pK\n",
 		      proc->pid, size, buffer);
@@ -879,60 +884,69 @@ static struct binder_buffer *binder_alloc_buf(struct binder_proc *proc,
 	}
 
 	return buffer;
+
+err_alloc_buf_struct_failed:
+	binder_update_page_range(proc, 0,
+				 (void *)PAGE_ALIGN((uintptr_t)buffer->data),
+				 end_page_addr, NULL);
+	return NULL;
 }
 
 static void *buffer_start_page(struct binder_buffer *buffer)
 {
-	return (void *)((uintptr_t)buffer & PAGE_MASK);
+	return (void *)((uintptr_t)buffer->data & PAGE_MASK);
 }
 
-static void *buffer_end_page(struct binder_buffer *buffer)
+static void *prev_buffer_end_page(struct binder_buffer *buffer)
 {
-	return (void *)(((uintptr_t)(buffer + 1) - 1) & PAGE_MASK);
+	return (void *)(((uintptr_t)(buffer->data) - 1) & PAGE_MASK);
 }
 
 static void binder_delete_free_buffer(struct binder_proc *proc,
 				      struct binder_buffer *buffer)
 {
 	struct binder_buffer *prev, *next = NULL;
-	int free_page_end = 1;
-	int free_page_start = 1;
-
+	bool to_free = true;
 	BUG_ON(proc->buffers.next == &buffer->entry);
 	prev = binder_buffer_prev(buffer);
 	BUG_ON(!prev->free);
-	if (buffer_end_page(prev) == buffer_start_page(buffer)) {
-		free_page_start = 0;
-		if (buffer_end_page(prev) == buffer_end_page(buffer))
-			free_page_end = 0;
+	if (prev_buffer_end_page(prev) == buffer_start_page(buffer)) {
+		to_free = false;
 		binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
 			     "%d: merge free, buffer %pK share page with %pK\n",
-			      proc->pid, buffer, prev);
+			     proc->pid, buffer->data, prev->data);
 	}
 
 	if (!list_is_last(&buffer->entry, &proc->buffers)) {
 		next = binder_buffer_next(buffer);
-		if (buffer_start_page(next) == buffer_end_page(buffer)) {
-			free_page_end = 0;
-			if (buffer_start_page(next) ==
-			    buffer_start_page(buffer))
-				free_page_start = 0;
+		if (buffer_start_page(next) == buffer_start_page(buffer)) {
+			to_free = false;
 			binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
 				     "%d: merge free, buffer %pK share page with %pK\n",
-				      proc->pid, buffer, prev);
+				     proc->pid,
+				     buffer->data,
+				     next->data);
 		}
 	}
-	list_del(&buffer->entry);
-	if (free_page_start || free_page_end) {
+
+	if (PAGE_ALIGNED(buffer->data)) {
+		binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
+			     "%d: merge free, buffer start %pK is page aligned\n",
+			     proc->pid, buffer->data);
+		to_free = false;
+	}
+
+	if (to_free) {
 		binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-			     "%d: merge free, buffer %pK do not share page%s%s with %pK or %pK\n",
-			     proc->pid, buffer, free_page_start ? "" : " end",
-			     free_page_end ? "" : " start", prev, next);
-		binder_update_page_range(proc, 0, free_page_start ?
-			buffer_start_page(buffer) : buffer_end_page(buffer),
-			(free_page_end ? buffer_end_page(buffer) :
-			buffer_start_page(buffer)) + PAGE_SIZE, NULL);
+			     "%d: merge free, buffer %pK do not share page with %pK or %pK\n",
+			     proc->pid, buffer->data,
+			     prev->data, next->data);
+		binder_update_page_range(proc, 0, buffer_start_page(buffer),
+					 buffer_start_page(buffer) + PAGE_SIZE,
+					 NULL);
 	}
+	list_del(&buffer->entry);
+	kfree(buffer);
 }
 
 static void binder_free_buf(struct binder_proc *proc,
@@ -953,8 +967,8 @@ static void binder_free_buf(struct binder_proc *proc,
 	BUG_ON(buffer->free);
 	BUG_ON(size > buffer_size);
 	BUG_ON(buffer->transaction != NULL);
-	BUG_ON((void *)buffer < proc->buffer);
-	BUG_ON((void *)buffer > proc->buffer + proc->buffer_size);
+	BUG_ON(buffer->data < proc->buffer);
+	BUG_ON(buffer->data > proc->buffer + proc->buffer_size);
 
 	if (buffer->async_transaction) {
 		proc->free_async_space += size + sizeof(struct binder_buffer);
@@ -3553,6 +3567,13 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_ops = &binder_vm_ops;
 	vma->vm_private_data = proc;
 
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		failure_string = "alloc buffer struct";
+		goto err_alloc_buf_struct_failed;
+	}
+
 	/* binder_update_page_range assumes preemption is disabled */
 	preempt_disable();
 	ret = __binder_update_page_range(proc, 1, proc->buffer,
@@ -3563,8 +3584,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
 		failure_string = "alloc small buf";
 		goto err_alloc_small_buf_failed;
 	}
-	buffer = proc->buffer;
-	INIT_LIST_HEAD(&proc->buffers);
+	buffer->data = proc->buffer;
 	list_add(&buffer->entry, &proc->buffers);
 	buffer->free = 1;
 	binder_insert_free_buffer(proc, buffer);
@@ -3579,6 +3599,8 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
 	return 0;
 
 err_alloc_small_buf_failed:
+	kfree(buffer);
+err_alloc_buf_struct_failed:
 	kfree(proc->pages);
 	proc->pages = NULL;
 err_alloc_pages_failed:
@@ -3613,6 +3635,7 @@ static int binder_open(struct inode *nodp, struct file *filp)
 	binder_dev = container_of(filp->private_data, struct binder_device,
 				  miscdev);
 	proc->context = &binder_dev->context;
+	INIT_LIST_HEAD(&proc->buffers);
 
 	binder_lock(__func__);
 
@@ -3733,6 +3756,7 @@ static void binder_deferred_release(struct binder_proc *proc)
 	struct binder_transaction *t;
 	struct binder_context *context = proc->context;
 	struct rb_node *n;
+	struct binder_buffer *buffer;
 	int threads, nodes, incoming_refs, outgoing_refs, buffers,
 		active_transactions, page_count;
 
@@ -3784,8 +3808,6 @@ static void binder_deferred_release(struct binder_proc *proc)
 
 	buffers = 0;
 	while ((n = rb_first(&proc->allocated_buffers))) {
-		struct binder_buffer *buffer;
-
 		buffer = rb_entry(n, struct binder_buffer, rb_node);
 
 		t = buffer->transaction;
@@ -3803,6 +3825,16 @@ static void binder_deferred_release(struct binder_proc *proc)
 
 	binder_stats_deleted(BINDER_STAT_PROC);
 
+	while (!list_empty(&proc->buffers)) {
+		buffer = list_first_entry(&proc->buffers,
+					  struct binder_buffer, entry);
+		WARN_ON(!buffer->free);
+
+		list_del(&buffer->entry);
+		WARN_ON_ONCE(!list_empty(&proc->buffers));
+		kfree(buffer);
+	}
+
 	page_count = 0;
 	if (proc->pages) {
 		int i;