linux-ext4 - Re: [PATCH 2/2] fscrypto: don't use on-stack buffer for key derivation

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Message-ID: <20161115185309.GE127180@google.com>
Date:   Tue, 15 Nov 2016 10:53:09 -0800
From:   Eric Biggers <ebiggers@...gle.com>
To:     Theodore Ts'o <tytso@....edu>
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 2/2] fscrypto: don't use on-stack buffer for key
 derivation

On Tue, Nov 15, 2016 at 11:47:04AM -0500, Theodore Ts'o wrote:
> On Thu, Nov 03, 2016 at 03:03:02PM -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.  get_crypt_info() was using a stack buffer to hold the
> > output from the encryption operation used to derive the per-file key.
> > Fix it by using a heap buffer.
> > 
> > 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

Hi Ted,

Would it make any sense to send these two patches to Linus for v4.9-rc6, given
that they fix bugs introduced in 4.9 with the virtually-mapped stack feature?
Or would you prefer to wait and have them go to 4.9 via stable?
Note that CONFIG_VMAP_STACK defaults to y on x86_64.

Thanks,

Eric
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