linux-kernel - Re: [PATCH] KEYS: user: Align the payload buffer

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Message-ID: <20190219230800.GD12177@gmail.com>
Date:   Tue, 19 Feb 2019 15:08:01 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     keyrings@...r.kernel.org, David Howells <dhowells@...hat.com>
Cc:     Aaro Koskinen <aaro.koskinen@....fi>,
        linux-fscrypt@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KEYS: user: Align the payload buffer

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@...gle.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@....fi>
> > Fixes: 2aa349f6e37c ("[PATCH] Keys: Export user-defined keyring operations")
> > Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@...gle.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.