Messages in this thread | | | Date | Mon, 23 Apr 2018 21:50:15 -0700 | From | Eric Biggers <> | Subject | Re: [PATCH 1/3] big key: get rid of stack array allocation |
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Hi Tycho,
On Mon, Apr 23, 2018 at 07:03:19PM -0600, Tycho Andersen wrote: > We're interested in getting rid of all of the stack allocated arrays in the > kernel [1]. This patch simply hardcodes the iv length to match that of the > hardcoded cipher. > > [1]: https://lkml.org/lkml/2018/3/7/621 > > v2: hardcode the length of the nonce to be the GCM AES IV length, and do a > sanity check in init(), Eric Biggers > > Signed-off-by: Tycho Andersen <tycho@tycho.ws> > CC: David Howells <dhowells@redhat.com> > CC: James Morris <jmorris@namei.org> > CC: "Serge E. Hallyn" <serge@hallyn.com> > CC: Jason A. Donenfeld <Jason@zx2c4.com> > CC: Eric Biggers <ebiggers3@gmail.com> > --- > security/keys/big_key.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/security/keys/big_key.c b/security/keys/big_key.c > index 933623784ccd..75c46786a166 100644 > --- a/security/keys/big_key.c > +++ b/security/keys/big_key.c > @@ -22,6 +22,7 @@ > #include <keys/user-type.h> > #include <keys/big_key-type.h> > #include <crypto/aead.h> > +#include <crypto/gcm.h> > > struct big_key_buf { > unsigned int nr_pages; > @@ -109,7 +110,7 @@ static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t dat > * an .update function, so there's no chance we'll wind up reusing the > * key to encrypt updated data. Simply put: one key, one encryption. > */ > - u8 zero_nonce[crypto_aead_ivsize(big_key_aead)]; > + u8 zero_nonce[GCM_AES_IV_SIZE]; > > aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL); > if (!aead_req) > @@ -425,6 +426,12 @@ static int __init big_key_init(void) > pr_err("Can't alloc crypto: %d\n", ret); > return ret; > } > + > + if (unlikely(crypto_aead_ivsize(big_key_aead) != GCM_AES_IV_SIZE)) { > + WARN(1, "big key algorithm changed?"); > + return -EINVAL; > + } > +
'big_key_aead' needs to be freed on error.
err = -EINVAL; goto free_aead;
Also how about defining the IV size next to the algorithm name? Then all the algorithm details would be on adjacent lines:
static const char big_key_alg_name[] = "gcm(aes)"; #define BIG_KEY_IV_SIZE GCM_AES_IV_SIZE
- Eric
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