net: usbnet: Fix the wrong netif_carrier_on() call

The commit referenced in the Fixes tag causes usbnet to malfunction
(identified via git bisect). Post-commit, my external RJ45 LAN cable
fails to connect. Linus also reported the same issue after pulling that
commit.

The code has a logic error: netif_carrier_on() is only called when the
link is already on. Fix this by moving the netif_carrier_on() call
outside the if-statement entirely. This ensures it is always called
when EVENT_LINK_CARRIER_ON is set and properly clears it regardless
of the link state.

Cc: stable@vger.kernel.org
Cc: Armando Budianto <sprite@gnuweeb.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/CAHk-=wjqL4uF0MG_c8+xHX1Vv8==sPYQrtzbdA3kzi96284nuQ@mail.gmail.com
Closes: https://lore.kernel.org/netdev/CAHk-=wjKh8X4PT_mU1kD4GQrbjivMfPn-_hXa6han_BTDcXddw@mail.gmail.com
Closes: https://lore.kernel.org/netdev/0752dee6-43d6-4e1f-81d2-4248142cccd2@gnuweeb.org
Fixes: 0d9cfc9b8cb1 ("net: usbnet: Avoid potential RCU stall on LINK_CHANGE event")
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index a38ffbf4b3f033d628609c692e49e0deec7f9be6..511c4154cf742b1222cfb89ef57747d61033631f 100644 (file)
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1120,6 +1120,9 @@ static void __handle_link_change(struct usbnet *dev)
        if (!test_bit(EVENT_DEV_OPEN, &dev->flags))
                return;
 
+       if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
+               netif_carrier_on(dev->net);
+
        if (!netif_carrier_ok(dev->net)) {
                /* kill URBs for reading packets to save bus bandwidth */
                unlink_urbs(dev, &dev->rxq);
@@ -1129,9 +1132,6 @@ static void __handle_link_change(struct usbnet *dev)
                 * tx queue is stopped by netcore after link becomes off
                 */
        } else {
-               if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
-                       netif_carrier_on(dev->net);
-
                /* submitting URBs for reading packets */
                queue_work(system_bh_wq, &dev->bh_work);
        }