Re: [PATCH] eCryptfs: Allocate sufficient buffer space for encrypted filename decoding

[Tyler Hicks <tyhicks@canonical.com>]

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On 2014-11-26 09:11:32, Michael Halcrow wrote:
> On Fri, Nov 21, 2014 at 9:02 AM, Michael Halcrow <mhalcrow@google.com> wrote:
> > Dmitry Chernenkov used KASAN to discover that eCryptfs writes past the
> > end of the allocated buffer during encrypted filename decoding. This
> > fix corrects the issue by ensuring that there is sufficient buffer
> > space allocated.
> >
> > Signed-off-by: Michael Halcrow <mhalcrow@google.com>
> > ---
> >  fs/ecryptfs/crypto.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> > index 2f6735d..53d4f2e 100644
> > --- a/fs/ecryptfs/crypto.c
> > +++ b/fs/ecryptfs/crypto.c
> > @@ -1871,7 +1871,7 @@ static size_t ecryptfs_max_decoded_size(size_t encoded_size)
> >          * the caller with the maximum amount of allocated
> >          * space that @dst will need to point to in a
> >          * subsequent call. */
> > -       return ((encoded_size + 1) * 3) / 4;
> > +       return (((encoded_size + 1) * 3) / 4) + 1;
> 
> Kees pointed out that the last write of 0 isn't even necessary.
> 
> Ignore this patch. I've sent out a fix that removes that write.

Agreed. I had been looking into this today and was about to say the same
thing. Thanks!

Tyler

> 
> >  }
> >
> >  /**
> > --
> > 2.1.0.rc2.206.gedb03e5
> >
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