linux-kernel - Re: [PATCH net v2] net: usbnet: Fix the wrong netif_carrier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wjqL4uF0MG_c8+xHX1Vv8==sPYQrtzbdA3kzi96284nuQ@mail.gmail.com>
Date: Wed, 6 Aug 2025 01:40:37 +0300
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Simon Horman <horms@...nel.org>
Cc: Ammar Faizi <ammarfaizi2@...weeb.org>, Oliver Neukum <oneukum@...e.com>, 
	Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Linux Netdev Mailing List <netdev@...r.kernel.org>, Linux USB Mailing List <linux-usb@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Armando Budianto <sprite@...weeb.org>, gwml@...r.gnuweeb.org, 
	stable@...r.kernel.org, John Ernberg <john.ernberg@...ia.se>
Subject: Re: [PATCH net v2] net: usbnet: Fix the wrong netif_carrier_on() call placement

On Tue, 5 Aug 2025 at 23:28, Simon Horman <horms@...nel.org> wrote:
>
> I have looked over the patch and it appears to me that it addresses a
> straightforward logic error: a check was added to turn the carrier on only
> if it is already on. Which seems a bit nonsensical. And presumably the
> intention was to add the check for the opposite case.
>
> This patch addresses that problem.

So I agree that there was a logic error.

I'm not 100% sure about the "straightforward" part.

In particular, the whole *rest* of the code in that

        if (!netif_carrier_ok(dev->net)) {

no longer makes sense after we've turned the link on with that

                if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
                        netif_carrier_on(dev->net);

sequence.

Put another way - once we've turned the carrier on, now that whole

                /* kill URBs for reading packets to save bus bandwidth */
                unlink_urbs(dev, &dev->rxq);

                /*
                 * tx_timeout will unlink URBs for sending packets and
                 * tx queue is stopped by netcore after link becomes off
                 */

thing makes no sense.

So my gut feel is that the

                if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
                        netif_carrier_on(dev->net);

should actually be done outside that if-statement entirely, because it
literally ends up changing the thing that if-statement is testing.

And no, I didn't actually test that version, because I was hoping that
somebody who actually knows this code better would pipe up.

                Linus