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Smack: Handle io_uring kernel thread privileges.

Message ID dacfb329-de66-d0cf-dcf9-f030ea1370de@schaufler-ca.com (mailing list archive)
State New
Headers show
Series Smack: Handle io_uring kernel thread privileges. | expand

Commit Message

Casey Schaufler Dec. 18, 2020, 1:12 a.m. UTC
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.

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(-)

Comments

Eric W. Biederman Dec. 21, 2020, 7:55 p.m. UTC | #1
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());
Jens Axboe Dec. 22, 2020, 2:05 a.m. UTC | #2
On 12/17/20 6:12 PM, Casey Schaufler wrote:
> 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: Jens Axboe <axboe@kernel.dk>
diff mbox series

Patch

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());