From: Theodore Ts'o <tytso@mit.edu>
Subject: Re: [PATCH 1/2] fscrypto: don't use on-stack buffer for filename
 encryption
Date: Tue, 15 Nov 2016 11:46:54 -0500
Message-ID: <20161115164654.soyjb7eouxnp6gay@thunk.org>
References: <1478210582-86338-1-git-send-email-ebiggers@google.com>
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Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-crypto@vger.kernel.org, jaegeuk@kernel.org, richard@nod.at,
        luto@kernel.org
To: Eric Biggers <ebiggers@google.com>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
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On Thu, Nov 03, 2016 at 03:03:01PM -0700, Eric Biggers wrote:
> With the new (in 4.9) option to use a virtually-mapped stack
> (CONFIG_VMAP_STACK), stack buffers cannot be used as input/output for
> the scatterlist crypto API because they may not be directly mappable to
> struct page.  For short filenames, fname_encrypt() was encrypting a
> stack buffer holding the padded filename.  Fix it by encrypting the
> filename in-place in the output buffer, thereby making the temporary
> buffer unnecessary.
> 
> This bug could most easily be observed in a CONFIG_DEBUG_SG kernel
> because this allowed the BUG in sg_set_buf() to be triggered.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

This commit is on the fscrypt and dev branches on ext4.git.

     	       	      	      	      - Ted