linux-ext4 - Re: [PATCH 1/2] fscrypto: don't use on-stack buffer for filename encryption

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Message-ID: <20161115164654.soyjb7eouxnp6gay@thunk.org>
Date:   Tue, 15 Nov 2016 11:46:54 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Eric Biggers <ebiggers@...gle.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-crypto@...r.kernel.org, jaegeuk@...nel.org, richard@....at,
        luto@...nel.org
Subject: Re: [PATCH 1/2] fscrypto: don't use on-stack buffer for filename
 encryption

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@...gle.com>

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

     	       	      	      	      - Ted
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