Re: [PATCH] Revert "Smack: Handle io_uring kernel thread privileges"

From: Casey Schaufler
Date: Fri Mar 26 2021 - 12:01:19 EST


On 3/25/2021 5:42 PM, Jens Axboe wrote:
> This reverts commit 942cb357ae7d9249088e3687ee6a00ed2745a0c7.
>
> The io_uring PF_IO_WORKER threads no longer have PF_KTHREAD set, so no
> need to special case them for credential checks.

Could you cite the commit making that change?
I wouldn't want to see this change back-ported to a kernel
that doesn't have that change as well.

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