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Message-ID: <CACT4Y+Y-K+QTNw3ZokVrRz4pCvMUN6GqRjDGdd1H2M=Qp1GRYA@mail.gmail.com>
Date: Mon, 28 Dec 2015 14:39:43 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: syzkaller <syzkaller@...glegroups.com>
Cc: David Miller <davem@...emloft.net>, linux-crypto@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
Kostya Serebryany <kcc@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Sasha Levin <sasha.levin@...cle.com>,
Kees Cook <keescook@...gle.com>
Subject: Re: [PATCH v2] crypto: algif_skcipher - Require setkey before accept(2)
On Fri, Dec 25, 2015 at 8:40 AM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> Dmitry Vyukov <dvyukov@...gle.com> wrote:
>>
>> I am testing with your two patches:
>> crypto: algif_skcipher - Use new skcipher interface
>> crypto: algif_skcipher - Require setkey before accept(2)
>> on top of a88164345b81292b55a8d4829fdd35c8d611cd7d (Dec 23).
>
> You sent the email to everyone on the original CC list except me.
> Please don't do that.
Hi Herbert,
My email client just followed instructions in your email. You've said
to Reply-to: syzkaller@...glegroups.com.
This version of the patch does fix the crash.
Tested-by: Dmitry Vyukov <dvyukov@...gle.com>
However, crypto is still considerably unstable. I will post reports
that I see separately.
>> Now the following program causes a bunch of use-after-frees and them
>> kills kernel:
>
> Yes there is an obvious bug in the patch that Julia Lawall has
> responded to in another thread. Here is a fixed version.
>
> ---8<--
> Some cipher implementations will crash if you try to use them
> without calling setkey first. This patch adds a check so that
> the accept(2) call will fail with -ENOKEY if setkey hasn't been
> done on the socket yet.
>
> Cc: stable@...r.kernel.org
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
>
> diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
> index 5c756b3..f4431bc 100644
> --- a/crypto/algif_skcipher.c
> +++ b/crypto/algif_skcipher.c
> @@ -31,6 +31,11 @@ struct skcipher_sg_list {
> struct scatterlist sg[0];
> };
>
> +struct skcipher_tfm {
> + struct crypto_skcipher *skcipher;
> + bool has_key;
> +};
> +
> struct skcipher_ctx {
> struct list_head tsgl;
> struct af_alg_sgl rsgl;
> @@ -750,17 +755,41 @@ static struct proto_ops algif_skcipher_ops = {
>
> static void *skcipher_bind(const char *name, u32 type, u32 mask)
> {
> - return crypto_alloc_skcipher(name, type, mask);
> + struct skcipher_tfm *tfm;
> + struct crypto_skcipher *skcipher;
> +
> + tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
> + if (!tfm)
> + return ERR_PTR(-ENOMEM);
> +
> + skcipher = crypto_alloc_skcipher(name, type, mask);
> + if (IS_ERR(skcipher)) {
> + kfree(tfm);
> + return ERR_CAST(skcipher);
> + }
> +
> + tfm->skcipher = skcipher;
> +
> + return tfm;
> }
>
> static void skcipher_release(void *private)
> {
> - crypto_free_skcipher(private);
> + struct skcipher_tfm *tfm = private;
> +
> + crypto_free_skcipher(tfm->skcipher);
> + kfree(tfm);
> }
>
> static int skcipher_setkey(void *private, const u8 *key, unsigned int keylen)
> {
> - return crypto_skcipher_setkey(private, key, keylen);
> + struct skcipher_tfm *tfm = private;
> + int err;
> +
> + err = crypto_skcipher_setkey(tfm->skcipher, key, keylen);
> + tfm->has_key = !err;
> +
> + return err;
> }
>
> static void skcipher_wait(struct sock *sk)
> @@ -792,20 +821,25 @@ static int skcipher_accept_parent(void *private, struct sock *sk)
> {
> struct skcipher_ctx *ctx;
> struct alg_sock *ask = alg_sk(sk);
> - unsigned int len = sizeof(*ctx) + crypto_skcipher_reqsize(private);
> + struct skcipher_tfm *tfm = private;
> + struct crypto_skcipher *skcipher = tfm->skcipher;
> + unsigned int len = sizeof(*ctx) + crypto_skcipher_reqsize(skcipher);
> +
> + if (!tfm->has_key)
> + return -ENOKEY;
>
> ctx = sock_kmalloc(sk, len, GFP_KERNEL);
> if (!ctx)
> return -ENOMEM;
>
> - ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(private),
> + ctx->iv = sock_kmalloc(sk, crypto_skcipher_ivsize(skcipher),
> GFP_KERNEL);
> if (!ctx->iv) {
> sock_kfree_s(sk, ctx, len);
> return -ENOMEM;
> }
>
> - memset(ctx->iv, 0, crypto_skcipher_ivsize(private));
> + memset(ctx->iv, 0, crypto_skcipher_ivsize(skcipher));
>
> INIT_LIST_HEAD(&ctx->tsgl);
> ctx->len = len;
> @@ -818,7 +852,7 @@ static int skcipher_accept_parent(void *private, struct sock *sk)
>
> ask->private = ctx;
>
> - skcipher_request_set_tfm(&ctx->req, private);
> + skcipher_request_set_tfm(&ctx->req, skcipher);
> skcipher_request_set_callback(&ctx->req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> af_alg_complete, &ctx->completion);
>
> --
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
>
> --
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