crypto: algif - add and use sock_kzfree_s() instead of memzero_explicit()

Commit e1bd95bf7c ("crypto: algif - zeroize IV buffer") and
2a6af25bef ("crypto: algif - zeroize message digest buffer")
added memzero_explicit() calls on buffers that are later on
passed back to sock_kfree_s().

This is a discussed follow-up that, instead, extends the sock
API and adds sock_kzfree_s(), which internally uses kzfree()
instead of kfree() for passing the buffers back to slab.

Having sock_kzfree_s() allows to keep the changes more minimal
by just having a drop-in replacement instead of adding
memzero_explicit() calls everywhere before sock_kfree_s().

In kzfree(), the compiler is not allowed to optimize the memset()
away and thus there's no need for memzero_explicit(). Both,
sock_kfree_s() and sock_kzfree_s() are wrappers for
__sock_kfree_s() and call into kfree() resp. kzfree(); here,
__sock_kfree_s() needs to be explicitly inlined as we want the
compiler to optimize the call and condition away and thus it
produces e.g. on x86_64 the _same_ assembler output for
sock_kfree_s() before and after, and thus also allows for
avoiding code duplication.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Daniel Borkmann 2014-11-19 17:13:11 +01:00 committed by Herbert Xu
parent 5d26a105b5
commit 79e886599e
4 changed files with 24 additions and 10 deletions

View File

@ -258,10 +258,8 @@ static void hash_sock_destruct(struct sock *sk)
struct alg_sock *ask = alg_sk(sk);
struct hash_ctx *ctx = ask->private;
memzero_explicit(ctx->result,
crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
sock_kfree_s(sk, ctx->result,
crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
sock_kzfree_s(sk, ctx->result,
crypto_ahash_digestsize(crypto_ahash_reqtfm(&ctx->req)));
sock_kfree_s(sk, ctx, ctx->len);
af_alg_release_parent(sk);
}

View File

@ -566,8 +566,7 @@ static void skcipher_sock_destruct(struct sock *sk)
struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(&ctx->req);
skcipher_free_sgl(sk);
memzero_explicit(ctx->iv, crypto_ablkcipher_ivsize(tfm));
sock_kfree_s(sk, ctx->iv, crypto_ablkcipher_ivsize(tfm));
sock_kzfree_s(sk, ctx->iv, crypto_ablkcipher_ivsize(tfm));
sock_kfree_s(sk, ctx, ctx->len);
af_alg_release_parent(sk);
}

View File

@ -1588,6 +1588,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
int *errcode, int max_page_order);
void *sock_kmalloc(struct sock *sk, int size, gfp_t priority);
void sock_kfree_s(struct sock *sk, void *mem, int size);
void sock_kzfree_s(struct sock *sk, void *mem, int size);
void sk_send_sigurg(struct sock *sk);
/*

View File

@ -1713,18 +1713,34 @@ void *sock_kmalloc(struct sock *sk, int size, gfp_t priority)
}
EXPORT_SYMBOL(sock_kmalloc);
/*
* Free an option memory block.
/* Free an option memory block. Note, we actually want the inline
* here as this allows gcc to detect the nullify and fold away the
* condition entirely.
*/
void sock_kfree_s(struct sock *sk, void *mem, int size)
static inline void __sock_kfree_s(struct sock *sk, void *mem, int size,
const bool nullify)
{
if (WARN_ON_ONCE(!mem))
return;
kfree(mem);
if (nullify)
kzfree(mem);
else
kfree(mem);
atomic_sub(size, &sk->sk_omem_alloc);
}
void sock_kfree_s(struct sock *sk, void *mem, int size)
{
__sock_kfree_s(sk, mem, size, false);
}
EXPORT_SYMBOL(sock_kfree_s);
void sock_kzfree_s(struct sock *sk, void *mem, int size)
{
__sock_kfree_s(sk, mem, size, true);
}
EXPORT_SYMBOL(sock_kzfree_s);
/* It is almost wait_for_tcp_memory minus release_sock/lock_sock.
I think, these locks should be removed for datagram sockets.
*/