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Commit bde541a5 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by Greg Kroah-Hartman
Browse files

net: tls: avoid hanging tasks on the tx_lock 



commit f3221361dc85d4de22586ce8441ec2c67b454f5d upstream.

syzbot sent a hung task report and Eric explains that adversarial
receiver may keep RWIN at 0 for a long time, so we are not guaranteed
to make forward progress. Thread which took tx_lock and went to sleep
may not release tx_lock for hours. Use interruptible sleep where
possible and reschedule the work if it can't take the lock.

Testing: existing selftest passes

Reported-by: default avatar <syzbot+9c0268252b8ef967c62e@syzkaller.appspotmail.com>
Fixes: 79ffe608 ("net/tls: add a TX lock")
Link: https://lore.kernel.org/all/000000000000e412e905f5b46201@google.com/


Cc: stable@vger.kernel.org # wait 4 weeks
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230301002857.2101894-1-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d94fbfcd

net/tls/tls_sw.c

+19 −7
Original line number Diff line number Diff line
@@ -945,7 +945,9 @@ int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) 
	if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))

		return -EOPNOTSUPP;



	mutex_lock(&tls_ctx->tx_lock);

	ret = mutex_lock_interruptible(&tls_ctx->tx_lock);

	if (ret)

		return ret;

	lock_sock(sk);



	if (unlikely(msg->msg_controllen)) {
@@ -1279,7 +1281,9 @@ int tls_sw_sendpage(struct sock *sk, struct page *page, 
		      MSG_SENDPAGE_NOTLAST | MSG_SENDPAGE_NOPOLICY))

		return -EOPNOTSUPP;



	mutex_lock(&tls_ctx->tx_lock);

	ret = mutex_lock_interruptible(&tls_ctx->tx_lock);

	if (ret)

		return ret;

	lock_sock(sk);

	ret = tls_sw_do_sendpage(sk, page, offset, size, flags);

	release_sock(sk);
@@ -2263,11 +2267,19 @@ static void tx_work_handler(struct work_struct *work) 


	if (!test_and_clear_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask))

		return;

	mutex_lock(&tls_ctx->tx_lock);



	if (mutex_trylock(&tls_ctx->tx_lock)) {

		lock_sock(sk);

		tls_tx_records(sk, -1);

		release_sock(sk);

		mutex_unlock(&tls_ctx->tx_lock);

	} else if (!test_and_set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask)) {

		/* Someone is holding the tx_lock, they will likely run Tx

		 * and cancel the work on their way out of the lock section.

		 * Schedule a long delay just in case.

		 */

		schedule_delayed_work(&ctx->tx_work.work, msecs_to_jiffies(10));

	}

}



void tls_sw_write_space(struct sock *sk, struct tls_context *ctx)