linux-kernel - [PATCH 3.18 018/134] KEYS: user: Align the payload buffer

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Date:   Fri, 22 Mar 2019 12:13:51 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Aaro Koskinen <aaro.koskinen@....fi>,
        Eric Biggers <ebiggers@...gle.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <james.morris@...rosoft.com>
Subject: [PATCH 3.18 018/134] KEYS: user: Align the payload buffer

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@...gle.com>

commit cc1780fc42c76c705dd07ea123f1143dc5057630 upstream.

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>
Tested-by: Aaro Koskinen <aaro.koskinen@....fi>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: James Morris <james.morris@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -29,7 +29,7 @@
 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;