diff mbox series

KEYS: user: Align the payload buffer

Message ID 155066953188.21038.12015964986007814182.stgit@warthog.procyon.org.uk (mailing list archive)
State New, archived
Headers show
Series KEYS: user: Align the payload buffer | expand

Commit Message

David Howells Feb. 20, 2019, 1:32 p.m. UTC 
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(-)

Comments

David Laight Feb. 20, 2019, 1:52 p.m. UTC | #1 
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

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David Howells Feb. 20, 2019, 2:09 p.m. UTC | #2 
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
James Morris Feb. 20, 2019, 8:50 p.m. UTC | #3 
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?
David Howells Feb. 20, 2019, 9:37 p.m. UTC | #4 
James Morris <jmorris@namei.org> wrote:

> Should this first one go into -rc?

Yes please.

David
diff mbox series

Patch

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;