[PATCH] audit: watching subtrees
New kind of audit rule predicates: "object is visible in given subtree".
The part that can be sanely implemented, that is. Limitations:
* if you have hardlink from outside of tree, you'd better watch
it too (or just watch the object itself, obviously)
* if you mount something under a watched tree, tell audit
that new chunk should be added to watched subtrees
* if you umount something in a watched tree and it's still mounted
elsewhere, you will get matches on events happening there. New command
tells audit to recalculate the trees, trimming such sources of false
positives.
Note that it's _not_ about path - if something mounted in several places
(multiple mount, bindings, different namespaces, etc.), the match does
_not_ depend on which one we are using for access.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index df66a21..5d96f2c 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -87,7 +87,7 @@
#endif
};
-static DEFINE_MUTEX(audit_filter_mutex);
+DEFINE_MUTEX(audit_filter_mutex);
/* Inotify handle */
extern struct inotify_handle *audit_ih;
@@ -145,7 +145,7 @@
kfree(e);
}
-static inline void audit_free_rule_rcu(struct rcu_head *head)
+void audit_free_rule_rcu(struct rcu_head *head)
{
struct audit_entry *e = container_of(head, struct audit_entry, rcu);
audit_free_rule(e);
@@ -217,7 +217,7 @@
/* Unpack a filter field's string representation from user-space
* buffer. */
-static char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
+char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
{
char *str;
@@ -247,7 +247,7 @@
struct audit_field *f)
{
if (krule->listnr != AUDIT_FILTER_EXIT ||
- krule->watch || krule->inode_f)
+ krule->watch || krule->inode_f || krule->tree)
return -EINVAL;
krule->inode_f = f;
@@ -266,7 +266,7 @@
if (path[0] != '/' || path[len-1] == '/' ||
krule->listnr != AUDIT_FILTER_EXIT ||
op & ~AUDIT_EQUAL ||
- krule->inode_f || krule->watch) /* 1 inode # per rule, for hash */
+ krule->inode_f || krule->watch || krule->tree)
return -EINVAL;
watch = audit_init_watch(path);
@@ -622,6 +622,17 @@
goto exit_free;
}
break;
+ case AUDIT_DIR:
+ str = audit_unpack_string(&bufp, &remain, f->val);
+ if (IS_ERR(str))
+ goto exit_free;
+ entry->rule.buflen += f->val;
+
+ err = audit_make_tree(&entry->rule, str, f->op);
+ kfree(str);
+ if (err)
+ goto exit_free;
+ break;
case AUDIT_INODE:
err = audit_to_inode(&entry->rule, f);
if (err)
@@ -668,7 +679,7 @@
}
/* Pack a filter field's string representation into data block. */
-static inline size_t audit_pack_string(void **bufp, char *str)
+static inline size_t audit_pack_string(void **bufp, const char *str)
{
size_t len = strlen(str);
@@ -747,6 +758,11 @@
data->buflen += data->values[i] =
audit_pack_string(&bufp, krule->watch->path);
break;
+ case AUDIT_DIR:
+ data->buflen += data->values[i] =
+ audit_pack_string(&bufp,
+ audit_tree_path(krule->tree));
+ break;
case AUDIT_FILTERKEY:
data->buflen += data->values[i] =
audit_pack_string(&bufp, krule->filterkey);
@@ -795,6 +811,11 @@
if (strcmp(a->watch->path, b->watch->path))
return 1;
break;
+ case AUDIT_DIR:
+ if (strcmp(audit_tree_path(a->tree),
+ audit_tree_path(b->tree)))
+ return 1;
+ break;
case AUDIT_FILTERKEY:
/* both filterkeys exist based on above type compare */
if (strcmp(a->filterkey, b->filterkey))
@@ -897,6 +918,14 @@
new->inode_f = old->inode_f;
new->watch = NULL;
new->field_count = old->field_count;
+ /*
+ * note that we are OK with not refcounting here; audit_match_tree()
+ * never dereferences tree and we can't get false positives there
+ * since we'd have to have rule gone from the list *and* removed
+ * before the chunks found by lookup had been allocated, i.e. before
+ * the beginning of list scan.
+ */
+ new->tree = old->tree;
memcpy(new->fields, old->fields, sizeof(struct audit_field) * fcount);
/* deep copy this information, updating the se_rule fields, because
@@ -1217,6 +1246,7 @@
struct audit_entry *e;
struct audit_field *inode_f = entry->rule.inode_f;
struct audit_watch *watch = entry->rule.watch;
+ struct audit_tree *tree = entry->rule.tree;
struct nameidata *ndp = NULL, *ndw = NULL;
int h, err;
#ifdef CONFIG_AUDITSYSCALL
@@ -1238,6 +1268,9 @@
mutex_unlock(&audit_filter_mutex);
if (e) {
err = -EEXIST;
+ /* normally audit_add_tree_rule() will free it on failure */
+ if (tree)
+ audit_put_tree(tree);
goto error;
}
@@ -1259,6 +1292,13 @@
h = audit_hash_ino((u32)watch->ino);
list = &audit_inode_hash[h];
}
+ if (tree) {
+ err = audit_add_tree_rule(&entry->rule);
+ if (err) {
+ mutex_unlock(&audit_filter_mutex);
+ goto error;
+ }
+ }
if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
list_add_rcu(&entry->list, list);
@@ -1292,6 +1332,7 @@
struct audit_entry *e;
struct audit_field *inode_f = entry->rule.inode_f;
struct audit_watch *watch, *tmp_watch = entry->rule.watch;
+ struct audit_tree *tree = entry->rule.tree;
LIST_HEAD(inotify_list);
int h, ret = 0;
#ifdef CONFIG_AUDITSYSCALL
@@ -1336,6 +1377,9 @@
}
}
+ if (e->rule.tree)
+ audit_remove_tree_rule(&e->rule);
+
list_del_rcu(&e->list);
call_rcu(&e->rcu, audit_free_rule_rcu);
@@ -1354,6 +1398,8 @@
out:
if (tmp_watch)
audit_put_watch(tmp_watch); /* match initial get */
+ if (tree)
+ audit_put_tree(tree); /* that's the temporary one */
return ret;
}
@@ -1737,6 +1783,7 @@
{
struct audit_entry *entry, *n, *nentry;
struct audit_watch *watch;
+ struct audit_tree *tree;
int i, err = 0;
/* audit_filter_mutex synchronizes the writers */
@@ -1748,6 +1795,7 @@
continue;
watch = entry->rule.watch;
+ tree = entry->rule.tree;
nentry = audit_dupe_rule(&entry->rule, watch);
if (unlikely(IS_ERR(nentry))) {
/* save the first error encountered for the
@@ -1763,7 +1811,9 @@
list_add(&nentry->rule.rlist,
&watch->rules);
list_del(&entry->rule.rlist);
- }
+ } else if (tree)
+ list_replace_init(&entry->rule.rlist,
+ &nentry->rule.rlist);
list_replace_rcu(&entry->list, &nentry->list);
}
call_rcu(&entry->rcu, audit_free_rule_rcu);