Commit b5590270 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

netlink: hold nlk->cb_mutex longer in __netlink_dump_start() 



__netlink_dump_start() releases nlk->cb_mutex right before
calling netlink_dump() which grabs it again.

This seems dangerous, even if KASAN did not bother yet.

Add a @lock_taken parameter to netlink_dump() to let it
grab the mutex if called from netlink_recvmsg() only.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJiri Pirko <jiri@nvidia.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6647b338

net/netlink/af_netlink.c

+6 −7
Original line number Diff line number Diff line
@@ -130,7 +130,7 @@ static const char *const nlk_cb_mutex_key_strings[MAX_LINKS + 1] = { 
	"nlk_cb_mutex-MAX_LINKS"

};



static int netlink_dump(struct sock *sk);

static int netlink_dump(struct sock *sk, bool lock_taken);



/* nl_table locking explained:

 * Lookup and traversal are protected with an RCU read-side lock. Insertion
@@ -1987,7 +1987,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, 


	if (READ_ONCE(nlk->cb_running) &&

	    atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {

		ret = netlink_dump(sk);

		ret = netlink_dump(sk, false);

		if (ret) {

			WRITE_ONCE(sk->sk_err, -ret);

			sk_error_report(sk);
@@ -2196,7 +2196,7 @@ static int netlink_dump_done(struct netlink_sock *nlk, struct sk_buff *skb, 
	return 0;

}



static int netlink_dump(struct sock *sk)

static int netlink_dump(struct sock *sk, bool lock_taken)

{

	struct netlink_sock *nlk = nlk_sk(sk);

	struct netlink_ext_ack extack = {};
@@ -2208,6 +2208,7 @@ static int netlink_dump(struct sock *sk) 
	int alloc_min_size;

	int alloc_size;



	if (!lock_taken)

		mutex_lock(nlk->cb_mutex);

	if (!nlk->cb_running) {

		err = -EINVAL;
@@ -2365,9 +2366,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 
	WRITE_ONCE(nlk->cb_running, true);

	nlk->dump_done_errno = INT_MAX;



	mutex_unlock(nlk->cb_mutex);



	ret = netlink_dump(sk);

	ret = netlink_dump(sk, true);



	sock_put(sk);