linux-kernel - Re: [PATCH 1/3] binder: avoid potential data leakage when copying txn

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Message-ID: <20211124130104.GI6514@kadam>
Date:   Wed, 24 Nov 2021 16:01:04 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Todd Kjos <tkjos@...gle.com>
Cc:     gregkh@...uxfoundation.org, christian@...uner.io, arve@...roid.com,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        maco@...gle.com, joel@...lfernandes.org, kernel-team@...roid.com
Subject: Re: [PATCH 1/3] binder: avoid potential data leakage when copying txn

On Tue, Nov 23, 2021 at 11:17:35AM -0800, Todd Kjos wrote:
> Transactions are copied from the sender to the target
> first and objects like BINDER_TYPE_PTR and BINDER_TYPE_FDA
> are then fixed up. This means there is a short period where
> the sender's version of these objects are visible to the
> target prior to the fixups.
> 
> Instead of copying all of the data first, copy data only
> after any needed fixups have been applied.
> 

This patch needs a fixes tag.

So this patch basically fixes the simple part of the info leak and
patch 3 fixes the complicated part.  Have I understood that correctly?

> @@ -2956,7 +2984,11 @@ static void binder_transaction(struct binder_proc *proc,
>  			}
>  			ret = binder_translate_fd_array(fda, parent, t, thread,
>  							in_reply_to);
> -			if (ret < 0) {
> +			if (ret < 0 ||
> +			    binder_alloc_copy_to_buffer(&target_proc->alloc,
> +							t->buffer,
> +							object_offset,
> +							fda, sizeof(*fda))) {
>  				return_error = BR_FAILED_REPLY;
>  				return_error_param = ret;

"ret" is not a negative error code if binder_translate_fd_array()
succeeds but binder_alloc_copy_to_buffer() fails.


>  				return_error_line = __LINE__;
> @@ -3028,6 +3060,19 @@ static void binder_transaction(struct binder_proc *proc,
>  			goto err_bad_object_type;
>  		}
>  	}

regards,
dan carpenter