[PATCH] KEYS: user: Align the payload buffer

[PATCH] KEYS: user: Align the payload buffer

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Align the payload of "user" and "logon" keys so that users of the
keyrings service can access it as a struct that requires more than
2-byte alignment.  fscrypt currently does this which results in the read
of fscrypt_key::size being misaligned as it needs 4-byte alignment.

Align to __alignof__(u64) rather than __alignof__(long) since in the
future it's conceivable that people would use structs beginning with
u64, which on some platforms would require more than 'long' alignment.

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 include/keys/user-type.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/keys/user-type.h b/include/keys/user-type.h
index e098cbe27db54..12babe9915944 100644
--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -31,7 +31,7 @@
 struct user_key_payload {
 	struct rcu_head	rcu;		/* RCU destructor */
 	unsigned short	datalen;	/* length of this data */
-	char		data[0];	/* actual data */
+	char		data[0] __aligned(__alignof__(u64)); /* actual data */
 };
 
 extern struct key_type key_type_user;
-- 
2.20.1

Re: [PATCH] KEYS: user: Align the payload buffer

[Aaro Koskinen]

Hi,

On Mon, Jan 14, 2019 at 07:37:16PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Align the payload of "user" and "logon" keys so that users of the
> keyrings service can access it as a struct that requires more than
> 2-byte alignment.  fscrypt currently does this which results in the read
> of fscrypt_key::size being misaligned as it needs 4-byte alignment.
> 
> Align to __alignof__(u64) rather than __alignof__(long) since in the
> future it's conceivable that people would use structs beginning with
> u64, which on some platforms would require more than 'long' alignment.
> 
> Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
> Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>

This fixes the "unaligned access" dmesg spam on SPARC when using ext4
encryption.

Thanks,

A.

> ---
>  include/keys/user-type.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> index e098cbe27db54..12babe9915944 100644
> --- a/include/keys/user-type.h
> +++ b/include/keys/user-type.h
> @@ -31,7 +31,7 @@
>  struct user_key_payload {
>  	struct rcu_head	rcu;		/* RCU destructor */
>  	unsigned short	datalen;	/* length of this data */
> -	char		data[0];	/* actual data */
> +	char		data[0] __aligned(__alignof__(u64)); /* actual data */
>  };
>  
>  extern struct key_type key_type_user;
> -- 
> 2.20.1
> 

Re: [PATCH] KEYS: user: Align the payload buffer

[Eric Biggers]

On Mon, Jan 14, 2019 at 07:37:16PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Align the payload of "user" and "logon" keys so that users of the
> keyrings service can access it as a struct that requires more than
> 2-byte alignment.  fscrypt currently does this which results in the read
> of fscrypt_key::size being misaligned as it needs 4-byte alignment.
> 
> Align to __alignof__(u64) rather than __alignof__(long) since in the
> future it's conceivable that people would use structs beginning with
> u64, which on some platforms would require more than 'long' alignment.
> 
> Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
> Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  include/keys/user-type.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> index e098cbe27db54..12babe9915944 100644
> --- a/include/keys/user-type.h
> +++ b/include/keys/user-type.h
> @@ -31,7 +31,7 @@
>  struct user_key_payload {
>  	struct rcu_head	rcu;		/* RCU destructor */
>  	unsigned short	datalen;	/* length of this data */
> -	char		data[0];	/* actual data */
> +	char		data[0] __aligned(__alignof__(u64)); /* actual data */
>  };
>  
>  extern struct key_type key_type_user;
> -- 
> 2.20.1
> 

Ping.  David, are you planning to apply this?

- Eric

Re: [PATCH] KEYS: user: Align the payload buffer

[Eric Biggers]

On Thu, Feb 07, 2019 at 03:35:09PM -0800, Eric Biggers wrote:
> On Mon, Jan 14, 2019 at 07:37:16PM -0800, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > Align the payload of "user" and "logon" keys so that users of the
> > keyrings service can access it as a struct that requires more than
> > 2-byte alignment.  fscrypt currently does this which results in the read
> > of fscrypt_key::size being misaligned as it needs 4-byte alignment.
> > 
> > Align to __alignof__(u64) rather than __alignof__(long) since in the
> > future it's conceivable that people would use structs beginning with
> > u64, which on some platforms would require more than 'long' alignment.
> > 
> > Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
> > Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
> > Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > ---
> >  include/keys/user-type.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> > index e098cbe27db54..12babe9915944 100644
> > --- a/include/keys/user-type.h
> > +++ b/include/keys/user-type.h
> > @@ -31,7 +31,7 @@
> >  struct user_key_payload {
> >  	struct rcu_head	rcu;		/* RCU destructor */
> >  	unsigned short	datalen;	/* length of this data */
> > -	char		data[0];	/* actual data */
> > +	char		data[0] __aligned(__alignof__(u64)); /* actual data */
> >  };
> >  
> >  extern struct key_type key_type_user;
> > -- 
> > 2.20.1
> > 
> 
> Ping.  David, are you planning to apply this?
> 
> - Eric

Ping.

Re: [PATCH] KEYS: user: Align the payload buffer

[David Howells]

Sent on to James.

David

Re: [PATCH] KEYS: user: Align the payload buffer

[David Howells]

James Morris <jmorris@namei.org> wrote:

> Should this first one go into -rc?

Yes please.

David

Re: [PATCH] KEYS: user: Align the payload buffer

[James Morris]

On Wed, 20 Feb 2019, David Howells wrote:

> David Laight <David.Laight@ACULAB.COM> wrote:
> 
> > I'd make the 'datalen' field 'unsigned int' at the same time.
> > It will use some of the hole you've made and generate better
> > code on most arches.
> 
> Most arches?  I though most, if not all, arches had a load-word instruction.
> 
> Do you want to send me a patch for that?  I'd rather not alter this patch at
> this point.  I can pass the additional patch to James for the next merge
> window.

Should this first one go into -rc?


-- 
James Morris
<jmorris@namei.org>

Re: [PATCH] KEYS: user: Align the payload buffer

[David Howells]

David Laight <David.Laight@ACULAB.COM> wrote:

> I'd make the 'datalen' field 'unsigned int' at the same time.
> It will use some of the hole you've made and generate better
> code on most arches.

Most arches?  I though most, if not all, arches had a load-word instruction.

Do you want to send me a patch for that?  I'd rather not alter this patch at
this point.  I can pass the additional patch to James for the next merge
window.

David

RE: [PATCH] KEYS: user: Align the payload buffer

[David Laight]

From: David Howells
> Sent: 20 February 2019 13:32
> 
> From: Eric Biggers <ebiggers@google.com>
> 
> Align the payload of "user" and "logon" keys so that users of the
> keyrings service can access it as a struct that requires more than
> 2-byte alignment.  fscrypt currently does this which results in the read
> of fscrypt_key::size being misaligned as it needs 4-byte alignment.
> 
> Align to __alignof__(u64) rather than __alignof__(long) since in the
> future it's conceivable that people would use structs beginning with
> u64, which on some platforms would require more than 'long' alignment.
...
>  include/keys/user-type.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> index e098cbe27db5..12babe991594 100644
> --- a/include/keys/user-type.h
> +++ b/include/keys/user-type.h
> @@ -31,7 +31,7 @@
>  struct user_key_payload {
>  	struct rcu_head	rcu;		/* RCU destructor */
>  	unsigned short	datalen;	/* length of this data */
> -	char		data[0];	/* actual data */
> +	char		data[0] __aligned(__alignof__(u64)); /* actual data */
>  };

I'd make the 'datalen' field 'unsigned int' at the same time.
It will use some of the hole you've made and generate better
code on most arches.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

[PATCH] KEYS: user: Align the payload buffer

[David Howells]

From: Eric Biggers <ebiggers@google.com>

Align the payload of "user" and "logon" keys so that users of the
keyrings service can access it as a struct that requires more than
2-byte alignment.  fscrypt currently does this which results in the read
of fscrypt_key::size being misaligned as it needs 4-byte alignment.

Align to __alignof__(u64) rather than __alignof__(long) since in the
future it's conceivable that people would use structs beginning with
u64, which on some platforms would require more than 'long' alignment.

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/keys/user-type.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/keys/user-type.h b/include/keys/user-type.h
index e098cbe27db5..12babe991594 100644
--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -31,7 +31,7 @@
 struct user_key_payload {
 	struct rcu_head	rcu;		/* RCU destructor */
 	unsigned short	datalen;	/* length of this data */
-	char		data[0];	/* actual data */
+	char		data[0] __aligned(__alignof__(u64)); /* actual data */
 };
 
 extern struct key_type key_type_user;