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SubjectRe: [PATCH] KEYS: user: Align the payload buffer
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
>

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