selinux: don't pass in NULL avd to avc_has_perm_noaudit

Right now security_get_user_sids() will pass in a NULL avd pointer to
avc_has_perm_noaudit(), which then forces that function to have a dummy
entry for that case and just generally test it.

Don't do it.  The normal callers all pass a real avd pointer, and this
helper function is incredibly hot.  So don't make avc_has_perm_noaudit()
do conditional stuff that isn't needed for the common case.

This also avoids some duplicated stack space.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 11 deletions

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index fcb89cb0f223..d515b2128a4e 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -752,10 +752,9 @@ int avc_ss_reset(u32 seqno)
 int avc_has_perm_noaudit(u32 ssid, u32 tsid,
                          u16 tclass, u32 requested,
                          unsigned flags,
-                         struct av_decision *in_avd)
+                         struct av_decision *avd)
 {
         struct avc_node *node;
-        struct av_decision avd_entry, *avd;
         int rc = 0;
         u32 denied;
 
@@ -766,18 +765,11 @@ int avc_has_perm_noaudit(u32 ssid, u32 tsid,
         node = avc_lookup(ssid, tsid, tclass);
         if (unlikely(!node)) {
                 rcu_read_unlock();
-
-                if (in_avd)
-                        avd = in_avd;
-                else
-                        avd = &avd_entry;
-
                 security_compute_av(ssid, tsid, tclass, avd);
                 rcu_read_lock();
                 node = avc_insert(ssid, tsid, tclass, avd);
         } else {
-                if (in_avd)
-                        memcpy(in_avd, &node->ae.avd, sizeof(*in_avd));
+                memcpy(avd, &node->ae.avd, sizeof(*avd));
                 avd = &node->ae.avd;
         }
 
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index c3e4b52699f4..973e00e34fa9 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2217,10 +2217,11 @@ out_unlock:
                 goto out;
         }
         for (i = 0, j = 0; i < mynel; i++) {
+                struct av_decision dummy_avd;
                 rc = avc_has_perm_noaudit(fromsid, mysids[i],
                                           SECCLASS_PROCESS, /* kernel value */
                                           PROCESS__TRANSITION, AVC_STRICT,
-                                          NULL);
+                                          &dummy_avd);
                 if (!rc)
                         mysids2[j++] = mysids[i];
                 cond_resched();