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Commit 53591787 authored by Chenbo Feng's avatar Chenbo Feng Committed by Todd Kjos
Browse files

ANDROID: qtaguid: Fix the UAF probelm with tag_ref_tree 



When multiple threads is trying to tag/delete the same socket at the
same time, there is a chance the tag_ref_entry of the target socket to
be null before the uid_tag_data entry is freed. It is caused by the
ctrl_cmd_tag function where it doesn't correctly grab the spinlocks
when tagging a socket.

Signed-off-by: default avatarChenbo Feng <fengc@google.com>
Bug: 65853158
Change-Id: I5d89885918054cf835370a52bff2d693362ac5f0
parent faeb94c0

net/netfilter/xt_qtaguid.c

+11 −9
Original line number Diff line number Diff line
@@ -520,13 +520,11 @@ static struct tag_ref *get_tag_ref(tag_t full_tag, 


	DR_DEBUG("qtaguid: get_tag_ref(0x%llx)\n",

		 full_tag);

	spin_lock_bh(&uid_tag_data_tree_lock);

	tr_entry = lookup_tag_ref(full_tag, &utd_entry);

	BUG_ON(IS_ERR_OR_NULL(utd_entry));

	if (!tr_entry)

		tr_entry = new_tag_ref(full_tag, utd_entry);



	spin_unlock_bh(&uid_tag_data_tree_lock);

	if (utd_res)

		*utd_res = utd_entry;

	DR_DEBUG("qtaguid: get_tag_ref(0x%llx) utd=%p tr=%p\n",
@@ -2033,6 +2031,7 @@ static int ctrl_cmd_delete(const char *input) 


	/* Delete socket tags */

	spin_lock_bh(&sock_tag_list_lock);

	spin_lock_bh(&uid_tag_data_tree_lock);

	node = rb_first(&sock_tag_tree);

	while (node) {

		st_entry = rb_entry(node, struct sock_tag, sock_node);
@@ -2062,6 +2061,7 @@ static int ctrl_cmd_delete(const char *input) 
				list_del(&st_entry->list);

		}

	}

	spin_unlock_bh(&uid_tag_data_tree_lock);

	spin_unlock_bh(&sock_tag_list_lock);



	sock_tag_tree_erase(&st_to_free_tree);
@@ -2271,10 +2271,12 @@ static int ctrl_cmd_tag(const char *input) 
	full_tag = combine_atag_with_uid(acct_tag, uid_int);



	spin_lock_bh(&sock_tag_list_lock);

	spin_lock_bh(&uid_tag_data_tree_lock);

	sock_tag_entry = get_sock_stat_nl(el_socket->sk);

	tag_ref_entry = get_tag_ref(full_tag, &uid_tag_data_entry);

	if (IS_ERR(tag_ref_entry)) {

		res = PTR_ERR(tag_ref_entry);

		spin_unlock_bh(&uid_tag_data_tree_lock);

		spin_unlock_bh(&sock_tag_list_lock);

		goto err_put;

	}
@@ -2301,9 +2303,14 @@ static int ctrl_cmd_tag(const char *input) 
			pr_err("qtaguid: ctrl_tag(%s): "

			       "socket tag alloc failed\n",

			       input);

			BUG_ON(tag_ref_entry->num_sock_tags <= 0);

			tag_ref_entry->num_sock_tags--;

			free_tag_ref_from_utd_entry(tag_ref_entry,

						    uid_tag_data_entry);

			spin_unlock_bh(&uid_tag_data_tree_lock);

			spin_unlock_bh(&sock_tag_list_lock);

			res = -ENOMEM;

			goto err_tag_unref_put;

			goto err_put;

		}

		/*

		 * Hold the sk refcount here to make sure the sk pointer cannot
@@ -2313,7 +2320,6 @@ static int ctrl_cmd_tag(const char *input) 
		sock_tag_entry->sk = el_socket->sk;

		sock_tag_entry->pid = current->tgid;

		sock_tag_entry->tag = combine_atag_with_uid(acct_tag, uid_int);

		spin_lock_bh(&uid_tag_data_tree_lock);

		pqd_entry = proc_qtu_data_tree_search(

			&proc_qtu_data_tree, current->tgid);

		/*
@@ -2331,11 +2337,11 @@ static int ctrl_cmd_tag(const char *input) 
		else

			list_add(&sock_tag_entry->list,

				 &pqd_entry->sock_tag_list);

		spin_unlock_bh(&uid_tag_data_tree_lock);



		sock_tag_tree_insert(sock_tag_entry, &sock_tag_tree);

		atomic64_inc(&qtu_events.sockets_tagged);

	}

	spin_unlock_bh(&uid_tag_data_tree_lock);

	spin_unlock_bh(&sock_tag_list_lock);

	/* We keep the ref to the sk until it is untagged */

	CT_DEBUG("qtaguid: ctrl_tag(%s): done st@%p ...->sk_refcnt=%d\n",
@@ -2344,10 +2350,6 @@ static int ctrl_cmd_tag(const char *input) 
	sockfd_put(el_socket);

	return 0;



err_tag_unref_put:

	BUG_ON(tag_ref_entry->num_sock_tags <= 0);

	tag_ref_entry->num_sock_tags--;

	free_tag_ref_from_utd_entry(tag_ref_entry, uid_tag_data_entry);

err_put:

	CT_DEBUG("qtaguid: ctrl_tag(%s): done. ...->sk_refcnt=%d\n",

		 input, refcount_read(&el_socket->sk->sk_refcnt) - 1);