Re: [PATCH 1/2] ceph: avoid NULL pointer dereference in ceph_crypto_key_destroy()

[Ilya Dryomov <idryomov@xxxxxxxxx>]

On Sun, Feb 4, 2018 at 11:08 AM, Chengguang Xu <cgxu519@xxxxxxxxxx> wrote:
> There are many reasons of failure from get_secret(),
> so it's necessary to add a check before calling crypto_free_skcipher()
> in case of NULL pointer dereference.
>
> Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxx>
> ---
>  net/ceph/crypto.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/ceph/crypto.c b/net/ceph/crypto.c
> index bf9d079..bb1dc2d 100644
> --- a/net/ceph/crypto.c
> +++ b/net/ceph/crypto.c
> @@ -136,8 +136,10 @@ void ceph_crypto_key_destroy(struct ceph_crypto_key *key)
>         if (key) {
>                 kfree(key->key);
>                 key->key = NULL;
> -               crypto_free_skcipher(key->tfm);
> -               key->tfm = NULL;
> +               if (key->tfm) {
> +                       crypto_free_skcipher(key->tfm);
> +                       key->tfm = NULL;
> +               }
>         }
>  }

Hi Chengguang,

crypto_free_skcipher() can handle a NULL pointer just fine:

    void crypto_destroy_tfm(void *mem, struct crypto_tfm *tfm)
    {
            struct crypto_alg *alg;

            if (unlikely(!mem))
                    return;

Thanks,

                Ilya
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