selinux: add support for the io_uring access controls

This patch implements two new io_uring access controls, specifically
support for controlling the io_uring "personalities" and
IORING_SETUP_SQPOLL.  Controlling the sharing of io_urings themselves
is handled via the normal file/inode labeling and sharing mechanisms.

The io_uring { override_creds } permission restricts which domains
the subject domain can use to override it's own credentials.
Granting a domain the io_uring { override_creds } permission allows
it to impersonate another domain in io_uring operations.

The io_uring { sqpoll } permission restricts which domains can create
asynchronous io_uring polling threads.  This is important from a
security perspective as operations queued by this asynchronous thread
inherit the credentials of the thread creator by default; if an
io_uring is shared across process/domain boundaries this could result
in one domain impersonating another.  Controlling the creation of
sqpoll threads, and the sharing of io_urings across processes, allow
policy authors to restrict the ability of one domain to impersonate
another via io_uring.

As a quick summary, this patch adds a new object class with two
permissions:

 io_uring { override_creds sqpoll }

These permissions can be seen in the two simple policy statements
below:

  allow domA_t domB_t : io_uring { override_creds };
  allow domA_t self : io_uring { sqpoll };

Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 084757ff4390..698ccfdaf82d 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -254,6 +254,8 @@ struct security_class_mapping secclass_map[] = {
 	  { "integrity", "confidentiality", NULL } },
 	{ "anon_inode",
 	  { COMMON_FILE_PERMS, NULL } },
+	{ "io_uring",
+	  { "override_creds", "sqpoll", NULL } },
 	{ NULL }
   };