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To:     "SMACK-discuss@lists.01.org" <SMACK-discuss@lists.01.org>,
        Linux Security Module list 
        <linux-security-module@vger.kernel.org>
Cc:     Jens Axboe <axboe@kernel.dk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        LKML <linux-kernel@vger.kernel.org>
From:   Casey Schaufler <casey@schaufler-ca.com>
Subject: [PATCH] Smack: Handle io_uring kernel thread privileges.
Message-ID: <dacfb329-de66-d0cf-dcf9-f030ea1370de@schaufler-ca.com>
Date:   Thu, 17 Dec 2020 17:12:29 -0800
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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>
---
=C2=A0security/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 cre=
d *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)) =3D=3D PF_KTHREAD)
 		return true;
=20
 	return smack_privileged_cred(cap, current_cred());