diff options
authorDaniel Borkmann <dborkman@redhat.com>2014-11-19 16:13:11 (GMT)
committerHerbert Xu <herbert@gondor.apana.org.au>2014-11-25 14:50:39 (GMT)
commit79e886599e6416d0de26e8562e4464577d081c3d (patch)
parent5d26a105b5a73e5635eae0629b42fa0a90e07b7b (diff)
crypto: algif - add and use sock_kzfree_s() instead of memzero_explicit()
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 <davem@davemloft.net> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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);
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);
- 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);
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)
- * 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))
- 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);
+void sock_kzfree_s(struct sock *sk, void *mem, int size)
+ __sock_kfree_s(sk, mem, size, true);
/* It is almost wait_for_tcp_memory minus release_sock/lock_sock.
I think, these locks should be removed for datagram sockets.

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