[PATCH] fscrypt: remove CRYPTO_CTR dependency

[PATCH] fscrypt: remove CRYPTO_CTR dependency

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

fscrypt doesn't use the CTR mode of operation for anything, so there's
no need to select CRYPTO_CTR.  It was added by commit 71dea01ea2ed
("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is
enabled").  But, I've been unable to identify the arm64 crypto bug it
was supposedly working around.

I suspect the issue was seen only on some old Android device kernel
(circa 3.10?).  So if the fix wasn't mistaken, the real bug is probably
already fixed.  Or maybe it was actually a bug in a non-upstream crypto
driver.

So, remove the dependency.  If it turns out there's actually still a
bug, we'll fix it properly.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/Kconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
index 02b7d91c92310..284b589b4774d 100644
--- a/fs/crypto/Kconfig
+++ b/fs/crypto/Kconfig
@@ -6,7 +6,6 @@ config FS_ENCRYPTION
 	select CRYPTO_ECB
 	select CRYPTO_XTS
 	select CRYPTO_CTS
-	select CRYPTO_CTR
 	select CRYPTO_SHA256
 	select KEYS
 	help
-- 
2.19.0.rc2.392.g5ba43deb5a-goog

Re: [PATCH] fscrypt: remove CRYPTO_CTR dependency

[Ard Biesheuvel]

On 5 September 2018 at 21:24, Eric Biggers <ebiggers@kernel.org> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> fscrypt doesn't use the CTR mode of operation for anything, so there's
> no need to select CRYPTO_CTR.  It was added by commit 71dea01ea2ed
> ("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is
> enabled").  But, I've been unable to identify the arm64 crypto bug it
> was supposedly working around.
>
> I suspect the issue was seen only on some old Android device kernel
> (circa 3.10?).  So if the fix wasn't mistaken, the real bug is probably
> already fixed.  Or maybe it was actually a bug in a non-upstream crypto
> driver.
>
> So, remove the dependency.  If it turns out there's actually still a
> bug, we'll fix it properly.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

This may be related to

11e3b725cfc2 crypto: arm64/aes-blk - honour iv_out requirement in CBC
and CTR modes

given that the commit in question mentions CTS. How it actually works
around the issue is unclear to me, though.




> ---
>  fs/crypto/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> index 02b7d91c92310..284b589b4774d 100644
> --- a/fs/crypto/Kconfig
> +++ b/fs/crypto/Kconfig
> @@ -6,7 +6,6 @@ config FS_ENCRYPTION
>         select CRYPTO_ECB
>         select CRYPTO_XTS
>         select CRYPTO_CTS
> -       select CRYPTO_CTR
>         select CRYPTO_SHA256
>         select KEYS
>         help
> --
> 2.19.0.rc2.392.g5ba43deb5a-goog
>

Re: [PATCH] fscrypt: remove CRYPTO_CTR dependency

[Eric Biggers]

On Thu, Sep 06, 2018 at 12:43:41PM +0200, Ard Biesheuvel wrote:
> On 5 September 2018 at 21:24, Eric Biggers <ebiggers@kernel.org> wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > fscrypt doesn't use the CTR mode of operation for anything, so there's
> > no need to select CRYPTO_CTR.  It was added by commit 71dea01ea2ed
> > ("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is
> > enabled").  But, I've been unable to identify the arm64 crypto bug it
> > was supposedly working around.
> >
> > I suspect the issue was seen only on some old Android device kernel
> > (circa 3.10?).  So if the fix wasn't mistaken, the real bug is probably
> > already fixed.  Or maybe it was actually a bug in a non-upstream crypto
> > driver.
> >
> > So, remove the dependency.  If it turns out there's actually still a
> > bug, we'll fix it properly.
> >
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> 
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> 
> This may be related to
> 
> 11e3b725cfc2 crypto: arm64/aes-blk - honour iv_out requirement in CBC
> and CTR modes
> 
> given that the commit in question mentions CTS. How it actually works
> around the issue is unclear to me, though.
> 
> 
> 
> 
> > ---
> >  fs/crypto/Kconfig | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> > index 02b7d91c92310..284b589b4774d 100644
> > --- a/fs/crypto/Kconfig
> > +++ b/fs/crypto/Kconfig
> > @@ -6,7 +6,6 @@ config FS_ENCRYPTION
> >         select CRYPTO_ECB
> >         select CRYPTO_XTS
> >         select CRYPTO_CTS
> > -       select CRYPTO_CTR
> >         select CRYPTO_SHA256
> >         select KEYS
> >         help
> > --
> > 2.19.0.rc2.392.g5ba43deb5a-goog
> >

Ping.  Ted, can you consider applying this to the fscrypt tree for 4.21?

Thanks,

- Eric

Re: [PATCH] fscrypt: remove CRYPTO_CTR dependency

[Theodore Y. Ts'o]

On Tue, Dec 04, 2018 at 03:45:07PM -0800, Eric Biggers wrote:
> On Thu, Sep 06, 2018 at 12:43:41PM +0200, Ard Biesheuvel wrote:
> > On 5 September 2018 at 21:24, Eric Biggers <ebiggers@kernel.org> wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > >
> > > fscrypt doesn't use the CTR mode of operation for anything, so there's
> > > no need to select CRYPTO_CTR.  It was added by commit 71dea01ea2ed
> > > ("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is
> > > enabled").  But, I've been unable to identify the arm64 crypto bug it
> > > was supposedly working around.
> > >
> > > I suspect the issue was seen only on some old Android device kernel
> > > (circa 3.10?).  So if the fix wasn't mistaken, the real bug is probably
> > > already fixed.  Or maybe it was actually a bug in a non-upstream crypto
> > > driver.
> > >
> > > So, remove the dependency.  If it turns out there's actually still a
> > > bug, we'll fix it properly.
> > >
> > > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > 
> > Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Thanks, applied.

					- Ted