selinux: convert type_val_to_struct to flex_array

In rawhide type_val_to_struct will allocate 26848 bytes, an order 3
allocations.  While this hasn't been seen to fail it isn't outside the
realm of possibiliy on systems with severe memory fragmentation.  Convert
to flex_array so no allocation will ever be bigger than PAGE_SIZE.

Signed-off-by: Eric Paris <eparis@redhat.com>

3 files changed, 34 insertions, 13 deletions

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 6ad73e81da5c..af41fdfe1a71 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -307,7 +307,11 @@ static int type_index(void *key, void *datum, void *datap)
                     || typdatum->bounds > p->p_types.nprim)
                         return -EINVAL;
                 p->p_type_val_to_name[typdatum->value - 1] = key;
-                p->type_val_to_struct[typdatum->value - 1] = typdatum;
+                /* this flex array was all preallocated, this cannot fail */
+                if (flex_array_put_ptr(p->type_val_to_struct_array,
+                                       typdatum->value - 1, typdatum,
+                                       GFP_KERNEL | __GFP_ZERO))
+                        BUG();
         }
 
         return 0;
@@ -484,11 +488,17 @@ static int policydb_index_others(struct policydb *p)
         if (!p->user_val_to_struct)
                 goto out;
 
+        /* Yes, I want the sizeof the pointer, not the structure */
         rc = -ENOMEM;
-        p->type_val_to_struct =
-                kmalloc(p->p_types.nprim * sizeof(*(p->type_val_to_struct)),
-                        GFP_KERNEL);
-        if (!p->type_val_to_struct)
+        p->type_val_to_struct_array = flex_array_alloc(sizeof(struct type_datum *),
+                                                       p->p_types.nprim,
+                                                       GFP_KERNEL | __GFP_ZERO);
+        if (!p->type_val_to_struct_array)
+                goto out;
+
+        rc = flex_array_prealloc(p->type_val_to_struct_array, 0,
+                                 p->p_types.nprim - 1, GFP_KERNEL | __GFP_ZERO);
+        if (rc)
                 goto out;
 
         rc = -ENOMEM;
@@ -699,7 +709,8 @@ void policydb_destroy(struct policydb *p)
         kfree(p->class_val_to_struct);
         kfree(p->role_val_to_struct);
         kfree(p->user_val_to_struct);
-        kfree(p->type_val_to_struct);
+        if (p->type_val_to_struct_array)
+                flex_array_free(p->type_val_to_struct_array);
 
         avtab_destroy(&p->te_avtab);
 
@@ -1618,7 +1629,10 @@ static int type_bounds_sanity_check(void *key, void *datum, void *datap)
                         return -EINVAL;
                 }
 
-                upper = p->type_val_to_struct[upper->bounds - 1];
+                upper = flex_array_get_ptr(p->type_val_to_struct_array,
+                                           upper->bounds - 1);
+                BUG_ON(!upper);
+
                 if (upper->attribute) {
                         printk(KERN_ERR "SELinux: type %s: "
                                "bounded by attribute %s",
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 95d3d7de361e..9826a92a6b0c 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -217,7 +217,7 @@ struct policydb {
         struct class_datum **class_val_to_struct;
         struct role_datum **role_val_to_struct;
         struct user_datum **user_val_to_struct;
-        struct type_datum **type_val_to_struct;
+        struct flex_array *type_val_to_struct_array;
 
         /* type enforcement access vectors and transitions */
         struct avtab te_avtab;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index ab6dbce5fd2a..afcbc19817f7 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -530,12 +530,18 @@ static void type_attribute_bounds_av(struct context *scontext,
         struct context lo_scontext;
         struct context lo_tcontext;
         struct av_decision lo_avd;
-        struct type_datum *source
-                = policydb.type_val_to_struct[scontext->type - 1];
-        struct type_datum *target
-                = policydb.type_val_to_struct[tcontext->type - 1];
+        struct type_datum *source;
+        struct type_datum *target;
         u32 masked = 0;
 
+        source = flex_array_get_ptr(policydb.type_val_to_struct_array,
+                                    scontext->type - 1);
+        BUG_ON(!source);
+
+        target = flex_array_get_ptr(policydb.type_val_to_struct_array,
+                                    tcontext->type - 1);
+        BUG_ON(!target);
+
         if (source->bounds) {
                 memset(&lo_avd, 0, sizeof(lo_avd));
 
@@ -828,7 +834,8 @@ int security_bounded_transition(u32 old_sid, u32 new_sid)
 
         index = new_context->type;
         while (true) {
-                type = policydb.type_val_to_struct[index - 1];
+                type = flex_array_get_ptr(policydb.type_val_to_struct_array,
+                                          index - 1);
                 BUG_ON(!type);
 
                 /* not bounded anymore */