From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 11 Apr 2019 14:37:10 -0700 From: Eric Biggers Subject: Re: [PATCH] fscrypt: add memory barrier when loading essiv_hash_tfm Message-ID: <20190411213710.GF225654@gmail.com> References: <20190318172454.240412-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190318172454.240412-1-ebiggers@kernel.org> To: linux-fscrypt@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org List-ID: On Mon, Mar 18, 2019 at 10:24:54AM -0700, Eric Biggers wrote: > From: Eric Biggers > > Load 'essiv_hash_tfm' using smp_load_acquire() to guarantee that the > struct crypto_shash is seen as fully initialized before being used. > > Signed-off-by: Eric Biggers > --- > fs/crypto/keyinfo.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c > index ba74dafa18a3..d1f0f8369d51 100644 > --- a/fs/crypto/keyinfo.c > +++ b/fs/crypto/keyinfo.c > @@ -379,7 +379,7 @@ fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, > > static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) > { > - struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); > + struct crypto_shash *tfm = smp_load_acquire(&essiv_hash_tfm); > > /* init hash transform on demand */ > if (unlikely(!tfm)) { > -- > 2.21.0.225.g810b269d1ac-goog > Actually I think we only need a data dependency barrier here, so this patch isn't needed. See discussion of similar case at https://marc.info/?l=linux-fsdevel&m=155487269904655&w=2 - Eric