Commit e1bd95bf7c25 ("crypto: algif - zeroize IV buffer") and 2a6af25befd0 ("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 <da...@davemloft.net> Signed-off-by: Daniel Borkmann <dbork...@redhat.com> --- crypto/algif_hash.c | 6 ++---- crypto/algif_skcipher.c | 3 +-- include/net/sock.h | 1 + net/core/sock.c | 24 ++++++++++++++++++++---- 4 files changed, 24 insertions(+), 10 deletions(-) diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index f75db4c..e605039 100644 --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -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); } diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index 85e3bdb..3438996 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -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); } diff --git a/include/net/sock.h b/include/net/sock.h index 7db3db1..37d6cc5 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -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); /* diff --git a/net/core/sock.c b/net/core/sock.c index 15e0c67..04ce26a 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -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. */ -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html