binder: return errors from buffer copy functions

The buffer copy functions assumed the caller would ensure
correct alignment and that the memory to be copied was
completely within the binder buffer. There have been
a few cases discovered by syzkallar where a malformed
transaction created by a user could violated the
assumptions and resulted in a BUG_ON.

The fix is to remove the BUG_ON and always return the
error to be handled appropriately by the caller.

Acked-by: Martijn Coenen <maco@android.com>
Reported-by: syzbot+3ae18325f96190606754@syzkaller.appspotmail.com
Fixes: bde4a19fc04f ("binder: use userspace pointer as base of buffer space")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 23 insertions, 21 deletions

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index ce5603c2291c..6d79a1b0d446 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1119,15 +1119,16 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
 	return 0;
 }
 
-static void binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
-					bool to_buffer,
-					struct binder_buffer *buffer,
-					binder_size_t buffer_offset,
-					void *ptr,
-					size_t bytes)
+static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
+				       bool to_buffer,
+				       struct binder_buffer *buffer,
+				       binder_size_t buffer_offset,
+				       void *ptr,
+				       size_t bytes)
 {
 	/* All copies must be 32-bit aligned and 32-bit size */
-	BUG_ON(!check_buffer(alloc, buffer, buffer_offset, bytes));
+	if (!check_buffer(alloc, buffer, buffer_offset, bytes))
+		return -EINVAL;
 
 	while (bytes) {
 		unsigned long size;
@@ -1155,25 +1156,26 @@ static void binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
 		ptr = ptr + size;
 		buffer_offset += size;
 	}
+	return 0;
 }
 
-void binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
-				 struct binder_buffer *buffer,
-				 binder_size_t buffer_offset,
-				 void *src,
-				 size_t bytes)
+int binder_alloc_copy_to_buffer(struct binder_alloc *alloc,
+				struct binder_buffer *buffer,
+				binder_size_t buffer_offset,
+				void *src,
+				size_t bytes)
 {
-	binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
-				    src, bytes);
+	return binder_alloc_do_buffer_copy(alloc, true, buffer, buffer_offset,
+					   src, bytes);
 }
 
-void binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
-				   void *dest,
-				   struct binder_buffer *buffer,
-				   binder_size_t buffer_offset,
-				   size_t bytes)
+int binder_alloc_copy_from_buffer(struct binder_alloc *alloc,
+				  void *dest,
+				  struct binder_buffer *buffer,
+				  binder_size_t buffer_offset,
+				  size_t bytes)
 {
-	binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
-				    dest, bytes);
+	return binder_alloc_do_buffer_copy(alloc, false, buffer, buffer_offset,
+					   dest, bytes);
 }