[RFC PATCH] selinux: convert the policy type_attr_map to flex_array

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Current selinux policy can have over 3000 types.  The type_attr_map in
policy is an array sized by the number of types times sizeof(struct ebitmap)
(12 on x86_64).  Basic math tells us the array is going to be of length
3000 x 12 = 36,000 bytes.  The largest 'safe' allocation on a long running
system is 16k.  Most of the time a 32k allocation will work.  But on long
running systems a 64k allocation (what we need) can fail quite regularly.
In order to deal with this I am converting the type_attr_map to use
flex_arrays.  Let the library code deal with breaking this into PAGE_SIZE
pieces.

Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
---

 security/selinux/ss/policydb.c |   49 ++++++++++++++++++++++++++++++++--------
 security/selinux/ss/policydb.h |    4 ++-
 security/selinux/ss/services.c |    9 ++++++-
 3 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 863d70f..0b9b878 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -31,6 +31,7 @@
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/audit.h>
+#include <linux/flex_array.h>
 #include "security.h"
 
 #include "policydb.h"
@@ -738,11 +739,17 @@ void policydb_destroy(struct policydb *p)
 	hashtab_map(p->range_tr, range_tr_destroy, NULL);
 	hashtab_destroy(p->range_tr);
 
-	if (p->type_attr_map) {
-		for (i = 0; i < p->p_types.nprim; i++)
-			ebitmap_destroy(&p->type_attr_map[i]);
+	if (p->type_attr_map_array) {
+		for (i = 0; i < p->p_types.nprim; i++) {
+			struct ebitmap *e;
+
+			e = flex_array_get(p->type_attr_map_array, i);
+			if (!e)
+				continue;
+			ebitmap_destroy(e);
+		}
+		flex_array_free(p->type_attr_map_array);
 	}
-	kfree(p->type_attr_map);
 	ebitmap_destroy(&p->policycaps);
 	ebitmap_destroy(&p->permissive_map);
 
@@ -2242,19 +2249,35 @@ int policydb_read(struct policydb *p, void *fp)
 		goto bad;
 
 	rc = -ENOMEM;
-	p->type_attr_map = kmalloc(p->p_types.nprim * sizeof(struct ebitmap), GFP_KERNEL);
-	if (!p->type_attr_map)
+	p->type_attr_map_array = flex_array_alloc(sizeof(struct ebitmap),
+						  p->p_types.nprim,
+						  GFP_KERNEL | __GFP_ZERO);
+	if (!p->type_attr_map_array)
+		goto bad;
+
+	/* preallocate so we don't have to worry about the put ever failing */
+	rc = flex_array_prealloc(p->type_attr_map_array, 0, p->p_types.nprim - 1,
+				 GFP_KERNEL | __GFP_ZERO);
+	if (rc)
 		goto bad;
 
 	for (i = 0; i < p->p_types.nprim; i++) {
-		ebitmap_init(&p->type_attr_map[i]);
+		struct ebitmap e;
+
+		ebitmap_init(&e);
 		if (p->policyvers >= POLICYDB_VERSION_AVTAB) {
-			rc = ebitmap_read(&p->type_attr_map[i], fp);
+			rc = ebitmap_read(&e, fp);
 			if (rc)
 				goto bad;
 		}
 		/* add the type itself as the degenerate case */
-		rc = ebitmap_set_bit(&p->type_attr_map[i], i, 1);
+		rc = ebitmap_set_bit(&e, i, 1);
+		if (rc)
+			goto bad;
+
+		/* should never fail since we preallocated */
+		rc = flex_array_put(p->type_attr_map_array, i, &e,
+				    GFP_KERNEL | __GFP_ZERO);
 		if (rc)
 			goto bad;
 	}
@@ -3100,7 +3123,13 @@ int policydb_write(struct policydb *p, void *fp)
 		return rc;
 
 	for (i = 0; i < p->p_types.nprim; i++) {
-		rc = ebitmap_write(&p->type_attr_map[i], fp);
+		struct ebitmap *e;
+
+		e = flex_array_get(p->type_attr_map_array, i);
+		if (unlikely(!e))
+			BUG();
+
+		rc = ebitmap_write(e, fp);
 		if (rc)
 			return rc;
 	}
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 9cbf9df..e013654 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -24,6 +24,8 @@
 #ifndef _SS_POLICYDB_H_
 #define _SS_POLICYDB_H_
 
+#include <linux/flex_array.h>
+
 #include "symtab.h"
 #include "avtab.h"
 #include "sidtab.h"
@@ -246,7 +248,7 @@ struct policydb {
 	struct hashtab *range_tr;
 
 	/* type -> attribute reverse mapping */
-	struct ebitmap *type_attr_map;
+	struct flex_array *type_attr_map_array;
 
 	struct ebitmap policycaps;
 
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index a4ac232..20b10bf 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -50,6 +50,7 @@
 #include <linux/audit.h>
 #include <linux/mutex.h>
 #include <linux/selinux.h>
+#include <linux/flex_array.h>
 #include <net/netlabel.h>
 
 #include "flask.h"
@@ -627,8 +628,12 @@ static void context_struct_compute_av(struct context *scontext,
 	 */
 	avkey.target_class = tclass;
 	avkey.specified = AVTAB_AV;
-	sattr = &policydb.type_attr_map[scontext->type - 1];
-	tattr = &policydb.type_attr_map[tcontext->type - 1];
+	sattr = flex_array_get(policydb.type_attr_map_array, scontext->type - 1);
+	if (unlikely(!sattr))
+		BUG();
+	tattr = flex_array_get(policydb.type_attr_map_array, tcontext->type - 1);
+	if (unlikely(!tattr))
+		BUG();
 	ebitmap_for_each_positive_bit(sattr, snode, i) {
 		ebitmap_for_each_positive_bit(tattr, tnode, j) {
 			avkey.source_type = i + 1;


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