Re: [PATCH] Smack: Handle io_uring kernel thread privileges.

[ebiederm@xmission.com (Eric W. Biederman)]

Casey Schaufler <casey@schaufler-ca.com> writes:

> Smack assumes that kernel threads are privileged for smackfs
> operations. This was necessary because the credential of the
> kernel thread was not related to a user operation. With io_uring
> the credential does reflect a user's rights and can be used.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

>
> Suggested-by: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  security/smack/smack_access.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
> index efe2406a3960..7eabb448acab 100644
> --- a/security/smack/smack_access.c
> +++ b/security/smack/smack_access.c
> @@ -688,9 +688,10 @@ bool smack_privileged_cred(int cap, const struct cred *cred)
>  bool smack_privileged(int cap)
>  {
>  	/*
> -	 * All kernel tasks are privileged
> +	 * Kernel threads may not have credentials we can use.
> +	 * The io_uring kernel threads do have reliable credentials.
>  	 */
> -	if (unlikely(current->flags & PF_KTHREAD))
> +	if ((current->flags & (PF_KTHREAD | PF_IO_WORKER)) == PF_KTHREAD)
>  		return true;
>  
>  	return smack_privileged_cred(cap, current_cred());