Commit 0558226c authored by Wen Gu's avatar Wen Gu Committed by Jakub Kicinski
Browse files

net/smc: Fix slab-out-of-bounds issue in fallback 



syzbot reported a slab-out-of-bounds/use-after-free issue,
which was caused by accessing an already freed smc sock in
fallback-specific callback functions of clcsock.

This patch fixes the issue by restoring fallback-specific
callback functions to original ones and resetting clcsock
sk_user_data to NULL before freeing smc sock.

Meanwhile, this patch introduces sk_callback_lock to make
the access and assignment to sk_user_data mutually exclusive.

Reported-by: default avatar <syzbot+b425899ed22c6943e00b@syzkaller.appspotmail.com>
Fixes: 341adeec ("net/smc: Forward wakeup to smc socket waitqueue after fallback")
Link: https://lore.kernel.org/r/00000000000013ca8105d7ae3ada@google.com/


Signed-off-by: default avatarWen Gu <guwen@linux.alibaba.com>
Acked-by: default avatarKarsten Graul <kgraul@linux.ibm.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 97b9af7a

net/smc/af_smc.c

+57 −23
Original line number Diff line number Diff line
@@ -243,11 +243,27 @@ struct proto smc_proto6 = { 
};

EXPORT_SYMBOL_GPL(smc_proto6);



static void smc_fback_restore_callbacks(struct smc_sock *smc)

{

	struct sock *clcsk = smc->clcsock->sk;



	write_lock_bh(&clcsk->sk_callback_lock);

	clcsk->sk_user_data = NULL;



	smc_clcsock_restore_cb(&clcsk->sk_state_change, &smc->clcsk_state_change);

	smc_clcsock_restore_cb(&clcsk->sk_data_ready, &smc->clcsk_data_ready);

	smc_clcsock_restore_cb(&clcsk->sk_write_space, &smc->clcsk_write_space);

	smc_clcsock_restore_cb(&clcsk->sk_error_report, &smc->clcsk_error_report);



	write_unlock_bh(&clcsk->sk_callback_lock);

}



static void smc_restore_fallback_changes(struct smc_sock *smc)

{

	if (smc->clcsock->file) { /* non-accepted sockets have no file yet */

		smc->clcsock->file->private_data = smc->sk.sk_socket;

		smc->clcsock->file = NULL;

		smc_fback_restore_callbacks(smc);

	}

}
@@ -745,48 +761,57 @@ static void smc_fback_forward_wakeup(struct smc_sock *smc, struct sock *clcsk, 


static void smc_fback_state_change(struct sock *clcsk)

{

	struct smc_sock *smc =

		smc_clcsock_user_data(clcsk);

	struct smc_sock *smc;



	if (!smc)

		return;

	smc_fback_forward_wakeup(smc, clcsk, smc->clcsk_state_change);

	read_lock_bh(&clcsk->sk_callback_lock);

	smc = smc_clcsock_user_data(clcsk);

	if (smc)

		smc_fback_forward_wakeup(smc, clcsk,

					 smc->clcsk_state_change);

	read_unlock_bh(&clcsk->sk_callback_lock);

}



static void smc_fback_data_ready(struct sock *clcsk)

{

	struct smc_sock *smc =

		smc_clcsock_user_data(clcsk);

	struct smc_sock *smc;



	if (!smc)

		return;

	smc_fback_forward_wakeup(smc, clcsk, smc->clcsk_data_ready);

	read_lock_bh(&clcsk->sk_callback_lock);

	smc = smc_clcsock_user_data(clcsk);

	if (smc)

		smc_fback_forward_wakeup(smc, clcsk,

					 smc->clcsk_data_ready);

	read_unlock_bh(&clcsk->sk_callback_lock);

}



static void smc_fback_write_space(struct sock *clcsk)

{

	struct smc_sock *smc =

		smc_clcsock_user_data(clcsk);

	struct smc_sock *smc;



	if (!smc)

		return;

	smc_fback_forward_wakeup(smc, clcsk, smc->clcsk_write_space);

	read_lock_bh(&clcsk->sk_callback_lock);

	smc = smc_clcsock_user_data(clcsk);

	if (smc)

		smc_fback_forward_wakeup(smc, clcsk,

					 smc->clcsk_write_space);

	read_unlock_bh(&clcsk->sk_callback_lock);

}



static void smc_fback_error_report(struct sock *clcsk)

{

	struct smc_sock *smc =

		smc_clcsock_user_data(clcsk);

	struct smc_sock *smc;



	if (!smc)

		return;

	smc_fback_forward_wakeup(smc, clcsk, smc->clcsk_error_report);

	read_lock_bh(&clcsk->sk_callback_lock);

	smc = smc_clcsock_user_data(clcsk);

	if (smc)

		smc_fback_forward_wakeup(smc, clcsk,

					 smc->clcsk_error_report);

	read_unlock_bh(&clcsk->sk_callback_lock);

}



static void smc_fback_replace_callbacks(struct smc_sock *smc)

{

	struct sock *clcsk = smc->clcsock->sk;



	write_lock_bh(&clcsk->sk_callback_lock);

	clcsk->sk_user_data = (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);



	smc_clcsock_replace_cb(&clcsk->sk_state_change, smc_fback_state_change,
@@ -797,6 +822,8 @@ static void smc_fback_replace_callbacks(struct smc_sock *smc) 
			       &smc->clcsk_write_space);

	smc_clcsock_replace_cb(&clcsk->sk_error_report, smc_fback_error_report,

			       &smc->clcsk_error_report);



	write_unlock_bh(&clcsk->sk_callback_lock);

}



static int smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
@@ -2370,17 +2397,20 @@ static void smc_tcp_listen_work(struct work_struct *work) 


static void smc_clcsock_data_ready(struct sock *listen_clcsock)

{

	struct smc_sock *lsmc =

		smc_clcsock_user_data(listen_clcsock);

	struct smc_sock *lsmc;



	read_lock_bh(&listen_clcsock->sk_callback_lock);

	lsmc = smc_clcsock_user_data(listen_clcsock);

	if (!lsmc)

		return;

		goto out;

	lsmc->clcsk_data_ready(listen_clcsock);

	if (lsmc->sk.sk_state == SMC_LISTEN) {

		sock_hold(&lsmc->sk); /* sock_put in smc_tcp_listen_work() */

		if (!queue_work(smc_tcp_ls_wq, &lsmc->tcp_listen_work))

			sock_put(&lsmc->sk);

	}

out:

	read_unlock_bh(&listen_clcsock->sk_callback_lock);

}



static int smc_listen(struct socket *sock, int backlog)
@@ -2412,10 +2442,12 @@ static int smc_listen(struct socket *sock, int backlog) 
	/* save original sk_data_ready function and establish

	 * smc-specific sk_data_ready function

	 */

	write_lock_bh(&smc->clcsock->sk->sk_callback_lock);

	smc->clcsock->sk->sk_user_data =

		(void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY);

	smc_clcsock_replace_cb(&smc->clcsock->sk->sk_data_ready,

			       smc_clcsock_data_ready, &smc->clcsk_data_ready);

	write_unlock_bh(&smc->clcsock->sk->sk_callback_lock);



	/* save original ops */

	smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops;
@@ -2430,9 +2462,11 @@ static int smc_listen(struct socket *sock, int backlog) 


	rc = kernel_listen(smc->clcsock, backlog);

	if (rc) {

		write_lock_bh(&smc->clcsock->sk->sk_callback_lock);

		smc_clcsock_restore_cb(&smc->clcsock->sk->sk_data_ready,

				       &smc->clcsk_data_ready);

		smc->clcsock->sk->sk_user_data = NULL;

		write_unlock_bh(&smc->clcsock->sk->sk_callback_lock);

		goto out;

	}

	sk->sk_max_ack_backlog = backlog;

net/smc/smc_close.c

+2 −0
Original line number Diff line number Diff line
@@ -214,9 +214,11 @@ int smc_close_active(struct smc_sock *smc) 
		sk->sk_state = SMC_CLOSED;

		sk->sk_state_change(sk); /* wake up accept */

		if (smc->clcsock && smc->clcsock->sk) {

			write_lock_bh(&smc->clcsock->sk->sk_callback_lock);

			smc_clcsock_restore_cb(&smc->clcsock->sk->sk_data_ready,

					       &smc->clcsk_data_ready);

			smc->clcsock->sk->sk_user_data = NULL;

			write_unlock_bh(&smc->clcsock->sk->sk_callback_lock);

			rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR);

		}

		smc_close_cleanup_listen(sk);