[PATCH] Smack: Handle io_uring kernel thread privileges.

Casey Schaufler casey at schaufler-ca.com
Fri Dec 18 01:12:29 UTC 2020

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 at kernel.dk>
Signed-off-by: Casey Schaufler <casey at 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());

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