security: Fix hook iteration for secid_to_secctx

secid_to_secctx is not stackable, and since the BPF LSM registers this
hook by default, the call_int_hook logic is not suitable which
"bails-on-fail" and casues issues when other LSMs register this hook and
eventually breaks Audit.

In order to fix this, directly iterate over the security hooks instead
of using call_int_hook as suggested in:

https: //lore.kernel.org/bpf/9d0eb6c6-803a-ff3a-5603-9ad6d9edfc00@schaufler-ca.com/#t

Fixes: 98e828a0650f ("security: Refactor declaration of LSM hooks")
Fixes: 625236ba3832 ("security: Fix the default value of secid_to_secctx hook")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200520125616.193765-1-kpsingh@chromium.org

diff --git a/security/security.c b/security/security.c
index 7fed24b..51de970 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -1965,8 +1965,20 @@ EXPORT_SYMBOL(security_ismaclabel);
 
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
-       return call_int_hook(secid_to_secctx, -EOPNOTSUPP, secid, secdata,
-                               seclen);
+       struct security_hook_list *hp;
+       int rc;
+
+       /*
+        * Currently, only one LSM can implement secid_to_secctx (i.e this
+        * LSM hook is not "stackable").
+        */
+       hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) {
+               rc = hp->hook.secid_to_secctx(secid, secdata, seclen);
+               if (rc != LSM_RET_DEFAULT(secid_to_secctx))
+                       return rc;
+       }
+
+       return LSM_RET_DEFAULT(secid_to_secctx);
 }
 EXPORT_SYMBOL(security_secid_to_secctx);