Re: [PATCH 10/11] selinux: Implement the watch_key security hook [ver #7]

From: Stephen Smalley
Date: Fri Aug 30 2019 - 10:15:24 EST

On 8/30/19 9:58 AM, David Howells wrote:
Implement the watch_key security hook to make sure that a key grants the
caller View permission in order to set a watch on a key.

For the moment, the watch_devices security hook is left unimplemented as
it's not obvious what the object should be since the queue is global and
didn't previously exist.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>

security/selinux/hooks.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 74dd46de01b6..a63249ad98ab 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6533,6 +6533,17 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
*_buffer = context;
return rc;
+static int selinux_watch_key(struct key *key)
+ struct key_security_struct *ksec = key->security;
+ u32 sid = cred_sid(current_cred());

How does this differ from current_sid()?

And has current_sid() not been converted to use selinux_cred()? Looks like selinux_kernfs_init_security() also uses current_security() directly.

+ return avc_has_perm(&selinux_state,
+ sid, ksec->sid, SECCLASS_KEY, KEY_NEED_VIEW, NULL);
@@ -6965,6 +6976,9 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(key_free, selinux_key_free),
LSM_HOOK_INIT(key_permission, selinux_key_permission),
LSM_HOOK_INIT(key_getsecurity, selinux_key_getsecurity),
+ LSM_HOOK_INIT(watch_key, selinux_watch_key),