LSM: shrink sizeof LSM specific portion of common_audit_data

Linus found that the gigantic size of the common audit data caused a big
perf hit on something as simple as running stat() in a loop.  This patch
requires LSMs to declare the LSM specific portion separately rather than
doing it in a union.  Thus each LSM can be responsible for shrinking their
portion and don't have to pay a penalty just because other LSMs have a
bigger space requirement.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 16 deletions

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 1a70fa26da72..00f3860c2370 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -436,9 +436,9 @@ static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
 {
         struct common_audit_data *ad = a;
         audit_log_format(ab, "avc:  %s ",
-                         ad->selinux_audit_data.denied ? "denied" : "granted");
-        avc_dump_av(ab, ad->selinux_audit_data.tclass,
-                        ad->selinux_audit_data.audited);
+                         ad->selinux_audit_data->denied ? "denied" : "granted");
+        avc_dump_av(ab, ad->selinux_audit_data->tclass,
+                        ad->selinux_audit_data->audited);
         audit_log_format(ab, " for ");
 }
 
@@ -452,9 +452,9 @@ static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
 {
         struct common_audit_data *ad = a;
         audit_log_format(ab, " ");
-        avc_dump_query(ab, ad->selinux_audit_data.ssid,
-                           ad->selinux_audit_data.tsid,
-                           ad->selinux_audit_data.tclass);
+        avc_dump_query(ab, ad->selinux_audit_data->ssid,
+                           ad->selinux_audit_data->tsid,
+                           ad->selinux_audit_data->tclass);
 }
 
 /* This is the slow part of avc audit with big stack footprint */
@@ -464,10 +464,12 @@ static noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
                 unsigned flags)
 {
         struct common_audit_data stack_data;
+        struct selinux_audit_data sad = {0,};
 
         if (!a) {
                 a = &stack_data;
                 COMMON_AUDIT_DATA_INIT(a, NONE);
+                a->selinux_audit_data = &sad;
         }
 
         /*
@@ -481,12 +483,12 @@ static noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
             (flags & MAY_NOT_BLOCK))
                 return -ECHILD;
 
-        a->selinux_audit_data.tclass = tclass;
-        a->selinux_audit_data.requested = requested;
-        a->selinux_audit_data.ssid = ssid;
-        a->selinux_audit_data.tsid = tsid;
-        a->selinux_audit_data.audited = audited;
-        a->selinux_audit_data.denied = denied;
+        a->selinux_audit_data->tclass = tclass;
+        a->selinux_audit_data->requested = requested;
+        a->selinux_audit_data->ssid = ssid;
+        a->selinux_audit_data->tsid = tsid;
+        a->selinux_audit_data->audited = audited;
+        a->selinux_audit_data->denied = denied;
         a->lsm_pre_audit = avc_audit_pre_callback;
         a->lsm_post_audit = avc_audit_post_callback;
         common_lsm_audit(a);
@@ -523,7 +525,7 @@ inline int avc_audit(u32 ssid, u32 tsid,
         if (unlikely(denied)) {
                 audited = denied & avd->auditdeny;
                 /*
-                 * a->selinux_audit_data.auditdeny is TRICKY!  Setting a bit in
+                 * a->selinux_audit_data->auditdeny is TRICKY!  Setting a bit in
                  * this field means that ANY denials should NOT be audited if
                  * the policy contains an explicit dontaudit rule for that
                  * permission.  Take notice that this is unrelated to the
@@ -532,15 +534,15 @@ inline int avc_audit(u32 ssid, u32 tsid,
                  *
                  * denied == READ
                  * avd.auditdeny & ACCESS == 0 (not set means explicit rule)
-                 * selinux_audit_data.auditdeny & ACCESS == 1
+                 * selinux_audit_data->auditdeny & ACCESS == 1
                  *
                  * We will NOT audit the denial even though the denied
                  * permission was READ and the auditdeny checks were for
                  * ACCESS
                  */
                 if (a &&
-                    a->selinux_audit_data.auditdeny &&
-                    !(a->selinux_audit_data.auditdeny & avd->auditdeny))
+                    a->selinux_audit_data->auditdeny &&
+                    !(a->selinux_audit_data->auditdeny & avd->auditdeny))
                         audited = 0;
         } else if (result)
                 audited = denied = requested;