SELinux: add more validity checks on policy load

Add more validity checks at policy load time to reject malformed
policies and prevent subsequent out-of-range indexing when in permissive
mode.  Resolves the NULL pointer dereference reported in
https://bugzilla.redhat.com/show_bug.cgi?id=357541.

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index 7551af1..9e70a16 100644 (file)
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -325,7 +325,7 @@ static uint16_t spec_order[] = {
        AVTAB_MEMBER
 };
 
-int avtab_read_item(void *fp, u32 vers, struct avtab *a,
+int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
                    int (*insertf)(struct avtab *a, struct avtab_key *k,
                                   struct avtab_datum *d, void *p),
                    void *p)
@@ -333,10 +333,11 @@ int avtab_read_item(void *fp, u32 vers, struct avtab *a,
        __le16 buf16[4];
        u16 enabled;
        __le32 buf32[7];
-       u32 items, items2, val;
+       u32 items, items2, val, vers = pol->policyvers;
        struct avtab_key key;
        struct avtab_datum datum;
        int i, rc;
+       unsigned set;
 
        memset(&key, 0, sizeof(struct avtab_key));
        memset(&datum, 0, sizeof(struct avtab_datum));
@@ -420,12 +421,35 @@ int avtab_read_item(void *fp, u32 vers, struct avtab *a,
        key.target_class = le16_to_cpu(buf16[items++]);
        key.specified = le16_to_cpu(buf16[items++]);
 
+       if (!policydb_type_isvalid(pol, key.source_type) ||
+           !policydb_type_isvalid(pol, key.target_type) ||
+           !policydb_class_isvalid(pol, key.target_class)) {
+               printk(KERN_WARNING "security: avtab: invalid type or class\n");
+               return -1;
+       }
+
+       set = 0;
+       for (i = 0; i < ARRAY_SIZE(spec_order); i++) {
+               if (key.specified & spec_order[i])
+                       set++;
+       }
+       if (!set || set > 1) {
+               printk(KERN_WARNING
+                       "security:  avtab:  more than one specifier\n");
+               return -1;
+       }
+
        rc = next_entry(buf32, fp, sizeof(u32));
        if (rc < 0) {
                printk("security: avtab: truncated entry\n");
                return -1;
        }
        datum.data = le32_to_cpu(*buf32);
+       if ((key.specified & AVTAB_TYPE) &&
+           !policydb_type_isvalid(pol, datum.data)) {
+               printk(KERN_WARNING "security: avtab: invalid type\n");
+               return -1;
+       }
        return insertf(a, &key, &datum, p);
 }
 
@@ -435,7 +459,7 @@ static int avtab_insertf(struct avtab *a, struct avtab_key *k,
        return avtab_insert(a, k, d);
 }
 
-int avtab_read(struct avtab *a, void *fp, u32 vers)
+int avtab_read(struct avtab *a, void *fp, struct policydb *pol)
 {
        int rc;
        __le32 buf[1];
@@ -459,7 +483,7 @@ int avtab_read(struct avtab *a, void *fp, u32 vers)
                goto bad;
 
        for (i = 0; i < nel; i++) {
-               rc = avtab_read_item(fp,vers, a, avtab_insertf, NULL);
+               rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL);
                if (rc) {
                        if (rc == -ENOMEM)
                                printk(KERN_ERR "security: avtab: out of memory\n");

diff --git a/security/selinux/ss/avtab.h b/security/selinux/ss/avtab.h
index d8edf8c..8da6a84 100644 (file)
--- a/security/selinux/ss/avtab.h
+++ b/security/selinux/ss/avtab.h
@@ -64,12 +64,13 @@ struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k);
 void avtab_destroy(struct avtab *h);
 void avtab_hash_eval(struct avtab *h, char *tag);
 
-int avtab_read_item(void *fp, uint32_t vers, struct avtab *a,
+struct policydb;
+int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
                    int (*insert)(struct avtab *a, struct avtab_key *k,
                                  struct avtab_datum *d, void *p),
                    void *p);
 
-int avtab_read(struct avtab *a, void *fp, u32 vers);
+int avtab_read(struct avtab *a, void *fp, struct policydb *pol);
 
 struct avtab_node *avtab_insert_nonunique(struct avtab *h, struct avtab_key *key,
                                          struct avtab_datum *datum);

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index 45b93a8..50ad85d 100644 (file)
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -362,7 +362,8 @@ static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list *
        data.head = NULL;
        data.tail = NULL;
        for (i = 0; i < len; i++) {
-               rc = avtab_read_item(fp, p->policyvers, &p->te_cond_avtab, cond_insertf, &data);
+               rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
+                                    &data);
                if (rc)
                        return rc;
 

diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
index 9a11dea..fb5d70a 100644 (file)
--- a/security/selinux/ss/mls.c
+++ b/security/selinux/ss/mls.c
@@ -157,49 +157,55 @@ void mls_sid_to_context(struct context *context,
        return;
 }
 
+int mls_level_isvalid(struct policydb *p, struct mls_level *l)
+{
+       struct level_datum *levdatum;
+       struct ebitmap_node *node;
+       int i;
+
+       if (!l->sens || l->sens > p->p_levels.nprim)
+               return 0;
+       levdatum = hashtab_search(p->p_levels.table,
+                                 p->p_sens_val_to_name[l->sens - 1]);
+       if (!levdatum)
+               return 0;
+
+       ebitmap_for_each_positive_bit(&l->cat, node, i) {
+               if (i > p->p_cats.nprim)
+                       return 0;
+               if (!ebitmap_get_bit(&levdatum->level->cat, i)) {
+                       /*
+                        * Category may not be associated with
+                        * sensitivity.
+                        */
+                       return 0;
+               }
+       }
+
+       return 1;
+}
+
+int mls_range_isvalid(struct policydb *p, struct mls_range *r)
+{
+       return (mls_level_isvalid(p, &r->level[0]) &&
+               mls_level_isvalid(p, &r->level[1]) &&
+               mls_level_dom(&r->level[1], &r->level[0]));
+}
+
 /*
  * Return 1 if the MLS fields in the security context
  * structure `c' are valid.  Return 0 otherwise.
  */
 int mls_context_isvalid(struct policydb *p, struct context *c)
 {
-       struct level_datum *levdatum;
        struct user_datum *usrdatum;
-       struct ebitmap_node *node;
-       int i, l;
 
        if (!selinux_mls_enabled)
                return 1;
 
-       /*
-        * MLS range validity checks: high must dominate low, low level must
-        * be valid (category set <-> sensitivity check), and high level must
-        * be valid (category set <-> sensitivity check)
-        */
-       if (!mls_level_dom(&c->range.level[1], &c->range.level[0]))
-               /* High does not dominate low. */
+       if (!mls_range_isvalid(p, &c->range))
                return 0;
 
-       for (l = 0; l < 2; l++) {
-               if (!c->range.level[l].sens || c->range.level[l].sens > p->p_levels.nprim)
-                       return 0;
-               levdatum = hashtab_search(p->p_levels.table,
-                       p->p_sens_val_to_name[c->range.level[l].sens - 1]);
-               if (!levdatum)
-                       return 0;
-
-               ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
-                       if (i > p->p_cats.nprim)
-                               return 0;
-                       if (!ebitmap_get_bit(&levdatum->level->cat, i))
-                               /*
-                                * Category may not be associated with
-                                * sensitivity in low level.
-                                */
-                               return 0;
-               }
-       }
-
        if (c->role == OBJECT_R_VAL)
                return 1;
 

diff --git a/security/selinux/ss/mls.h b/security/selinux/ss/mls.h
index 096d1b4..ab53663 100644 (file)
--- a/security/selinux/ss/mls.h
+++ b/security/selinux/ss/mls.h
@@ -27,6 +27,8 @@
 int mls_compute_context_len(struct context *context);
 void mls_sid_to_context(struct context *context, char **scontext);
 int mls_context_isvalid(struct policydb *p, struct context *c);
+int mls_range_isvalid(struct policydb *p, struct mls_range *r);
+int mls_level_isvalid(struct policydb *p, struct mls_level *l);
 
 int mls_context_to_sid(char oldc,
                       char **scontext,

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 539828b..b582aae 100644 (file)
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -713,6 +713,27 @@ out:
        return rc;
 }
 
+int policydb_class_isvalid(struct policydb *p, unsigned int class)
+{
+       if (!class || class > p->p_classes.nprim)
+               return 0;
+       return 1;
+}
+
+int policydb_role_isvalid(struct policydb *p, unsigned int role)
+{
+       if (!role || role > p->p_roles.nprim)
+               return 0;
+       return 1;
+}
+
+int policydb_type_isvalid(struct policydb *p, unsigned int type)
+{
+       if (!type || type > p->p_types.nprim)
+               return 0;
+       return 1;
+}
+
 /*
  * Return 1 if the fields in the security context
  * structure `c' are valid.  Return 0 otherwise.
@@ -1260,6 +1281,7 @@ static int mls_read_level(struct mls_level *lp, void *fp)
                       "categories\n");
                goto bad;
        }
+
        return 0;
 
 bad:
@@ -1563,7 +1585,7 @@ int policydb_read(struct policydb *p, void *fp)
                p->symtab[i].nprim = nprim;
        }
 
-       rc = avtab_read(&p->te_avtab, fp, p->policyvers);
+       rc = avtab_read(&p->te_avtab, fp, p);
        if (rc)
                goto bad;
 
@@ -1595,6 +1617,12 @@ int policydb_read(struct policydb *p, void *fp)
                tr->role = le32_to_cpu(buf[0]);
                tr->type = le32_to_cpu(buf[1]);
                tr->new_role = le32_to_cpu(buf[2]);
+               if (!policydb_role_isvalid(p, tr->role) ||
+                   !policydb_type_isvalid(p, tr->type) ||
+                   !policydb_role_isvalid(p, tr->new_role)) {
+                       rc = -EINVAL;
+                       goto bad;
+               }
                ltr = tr;
        }
 
@@ -1619,6 +1647,11 @@ int policydb_read(struct policydb *p, void *fp)
                        goto bad;
                ra->role = le32_to_cpu(buf[0]);
                ra->new_role = le32_to_cpu(buf[1]);
+               if (!policydb_role_isvalid(p, ra->role) ||
+                   !policydb_role_isvalid(p, ra->new_role)) {
+                       rc = -EINVAL;
+                       goto bad;
+               }
                lra = ra;
        }
 
@@ -1872,9 +1905,19 @@ int policydb_read(struct policydb *p, void *fp)
                                rt->target_class = le32_to_cpu(buf[0]);
                        } else
                                rt->target_class = SECCLASS_PROCESS;
+                       if (!policydb_type_isvalid(p, rt->source_type) ||
+                           !policydb_type_isvalid(p, rt->target_type) ||
+                           !policydb_class_isvalid(p, rt->target_class)) {
+                               rc = -EINVAL;
+                               goto bad;
+                       }
                        rc = mls_read_range_helper(&rt->target_range, fp);
                        if (rc)
                                goto bad;
+                       if (!mls_range_isvalid(p, &rt->target_range)) {
+                               printk(KERN_WARNING "security:  rangetrans:  invalid range\n");
+                               goto bad;
+                       }
                        lrt = rt;
                }
        }

diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 844d310..ed6fc68 100644 (file)
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -251,6 +251,9 @@ struct policydb {
 extern void policydb_destroy(struct policydb *p);
 extern int policydb_load_isids(struct policydb *p, struct sidtab *s);
 extern int policydb_context_isvalid(struct policydb *p, struct context *c);
+extern int policydb_class_isvalid(struct policydb *p, unsigned int class);
+extern int policydb_type_isvalid(struct policydb *p, unsigned int type);
+extern int policydb_role_isvalid(struct policydb *p, unsigned int role);
 extern int policydb_read(struct policydb *p, void *fp);
 
 #define PERM_SYMTAB_SIZE 32