Commit febe8012 authored by Qingfang Deng's avatar Qingfang Deng Committed by Paolo Abeni
Browse files

ppp: remove pch->chan NULL checks from tx path 



Now that ppp_disconnect_channel() is called before pch->chan is set to
NULL, a channel from ppp->channels list on the transmit path is
guaranteed to have non-NULL pch->chan.

Remove the pch->chan NULL checks from ppp_push(), ppp_mp_explode(), and
ppp_fill_forward_path(), where a channel is obtained from the list.
Remove the corresponding WRITE/READ_ONCE annotations as they no longer
race.

Signed-off-by: default avatarQingfang Deng <dqfext@gmail.com>
Link: https://patch.msgid.link/20260312093732.277254-2-dqfext@gmail.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 6a196e83

drivers/net/ppp/ppp_generic.c

+21 −47
Original line number Diff line number Diff line
@@ -1602,10 +1602,7 @@ static int ppp_fill_forward_path(struct net_device_path_ctx *ctx, 
	if (!pch)

		return -ENODEV;



	chan = READ_ONCE(pch->chan);

	if (!chan)

		return -ENODEV;



	chan = pch->chan;

	if (!chan->ops->fill_forward_path)

		return -EOPNOTSUPP;
@@ -1928,9 +1925,9 @@ ppp_push(struct ppp *ppp, struct sk_buff *skb) 


		spin_lock(&pch->downl);

		chan = pch->chan;

		if (unlikely(!chan || (!chan->direct_xmit && skb_linearize(skb)))) {

			/* channel got unregistered, or it requires a linear

			 * skb but linearization failed

		if (unlikely(!chan->direct_xmit && skb_linearize(skb))) {

			/* channel requires a linear skb but linearization

			 * failed

			 */

			kfree_skb(skb);

			ret = 1;
@@ -1991,16 +1988,11 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) 
	hdrlen = (ppp->flags & SC_MP_XSHORTSEQ)? MPHDRLEN_SSN: MPHDRLEN;

	i = 0;

	list_for_each_entry(pch, &ppp->channels, clist) {

		if (pch->chan) {

		pch->avail = 1;

		navail++;

		pch->speed = pch->chan->speed;

		} else {

			pch->avail = 0;

		}

		if (pch->avail) {

			if (skb_queue_empty(&pch->file.xq) ||

				!pch->had_frag) {



		if (skb_queue_empty(&pch->file.xq) || !pch->had_frag) {

			if (pch->speed == 0)

				nzero++;

			else
@@ -2012,7 +2004,7 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) 
		}

		if (!pch->had_frag && i < ppp->nxchan)

			ppp->nxchan = i;

		}



		++i;

	}

	/*
@@ -2071,25 +2063,7 @@ static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb) 
			pch->avail = 1;

		}



		/* check the channel's mtu and whether it is still attached. */

		spin_lock(&pch->downl);

		if (pch->chan == NULL) {

			/* can't use this channel, it's being deregistered */

			if (pch->speed == 0)

				nzero--;

			else

				totspeed -= pch->speed;



			spin_unlock(&pch->downl);

			pch->avail = 0;

			totlen = len;

			totfree--;

			nfree--;

			if (--navail == 0)

				break;

			continue;

		}



		/*

		*if the channel speed is not set divide

		*the packet evenly among the free channels;
@@ -3035,7 +3009,7 @@ ppp_unregister_channel(struct ppp_channel *chan) 
	ppp_disconnect_channel(pch);

	down_write(&pch->chan_sem);

	spin_lock_bh(&pch->downl);

	WRITE_ONCE(pch->chan, NULL);

	pch->chan = NULL;

	spin_unlock_bh(&pch->downl);

	up_write(&pch->chan_sem);