Re: [tipc-discussion] [PATCH RFC 1/5] tipc: fix using smp_processor_id() in preemptible

[Jon M. <jm...@re...>]

On 7/10/20 6:11 AM, Tuong Lien wrote:
> The 'this_cpu_ptr()' is used to obtain the AEAD key' TFM on the current
> CPU for encryption, however the execution can be preemptible since it's
> actually user-space context, so the 'using smp_processor_id() in
> preemptible' has been observed.
>
> We fix the issue by using the 'get/put_cpu_ptr()' API which consists of
> a 'preempt_disable()' instead.
>
> Signed-off-by: Tuong Lien <tuo...@de...>
> ---
>   net/tipc/crypto.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index c8c47fc72653..1827ce4fac5d 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -326,7 +326,8 @@ static void tipc_aead_free(struct rcu_head *rp)
>   	if (aead->cloned) {
>   		tipc_aead_put(aead->cloned);
>   	} else {
> -		head = *this_cpu_ptr(aead->tfm_entry);
> +		head = *get_cpu_ptr(aead->tfm_entry);
> +		put_cpu_ptr(aead->tfm_entry);
>   		list_for_each_entry_safe(tfm_entry, tmp, &head->list, list) {
>   			crypto_free_aead(tfm_entry->tfm);
>   			list_del(&tfm_entry->list);
> @@ -399,10 +400,15 @@ static void tipc_aead_users_set(struct tipc_aead __rcu *aead, int val)
>    */
>   static struct crypto_aead *tipc_aead_tfm_next(struct tipc_aead *aead)
>   {
> -	struct tipc_tfm **tfm_entry = this_cpu_ptr(aead->tfm_entry);
> +	struct tipc_tfm **tfm_entry;
> +	struct crypto_aead *tfm;
>   
> +	tfm_entry = get_cpu_ptr(aead->tfm_entry);
>   	*tfm_entry = list_next_entry(*tfm_entry, list);
> -	return (*tfm_entry)->tfm;
> +	tfm = (*tfm_entry)->tfm;
> +	put_cpu_ptr(tfm_entry);
> +
> +	return tfm;
>   }
>   
>   /**
Acked-by: Jon Maloy <jm...@re...>

I think you should send this as a separate patch to 'net'.
Don't forget to add a "Fixes: ..." line to the commit log.

///jon