From: Sam Sun <samsun1006219@gmail.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
Greg KH <gregkh@linuxfoundation.org>,
swboyd@chromium.org, ricardo@marliere.net, hkallweit1@gmail.com,
heikki.krogerus@linux.intel.com, mathias.nyman@linux.intel.com,
royluo@google.com, syzkaller-bugs@googlegroups.com,
xrivendell7@gmail.com
Subject: Re: [Linux kernel bug] general protection fault in disable_store
Date: Tue, 16 Apr 2024 17:05:55 +0800 [thread overview]
Message-ID: <CAEkJfYMSwuikpBJudOaFYrxgf9e=_O4nig6sTPLLAtpdEKQuyQ@mail.gmail.com> (raw)
In-Reply-To: <5704ac63-5e5b-416c-a2a1-57528e76a02f@rowland.harvard.edu>
On Mon, Apr 15, 2024 at 10:47 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> Actually, I've got a completely different patch which I think will fix
> the problem you encountered. Instead of using mutual exclusion to
> avoid the race, it prevents the two routines from being called at the
> same time so the race can't occur in the first place. It also should
> guarantee the usb_hub_to_struct_hub() doesn't return NULL when
> disable_store() calls it.
>
> Can you try the patch below, instead of (not along with) the first
> patch? Thanks.
>
> Alan Stern
>
>
>
> Index: usb-devel/drivers/usb/core/hub.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/hub.c
> +++ usb-devel/drivers/usb/core/hub.c
> @@ -1788,16 +1788,15 @@ static void hub_disconnect(struct usb_in
>
> mutex_lock(&usb_port_peer_mutex);
>
> + for (port1 = hdev->maxchild; port1 > 0; --port1)
> + usb_hub_remove_port_device(hub, port1);
> +
> /* Avoid races with recursively_mark_NOTATTACHED() */
> spin_lock_irq(&device_state_lock);
> - port1 = hdev->maxchild;
> hdev->maxchild = 0;
> usb_set_intfdata(intf, NULL);
> spin_unlock_irq(&device_state_lock);
>
> - for (; port1 > 0; --port1)
> - usb_hub_remove_port_device(hub, port1);
> -
> mutex_unlock(&usb_port_peer_mutex);
>
> if (hub->hdev->speed == USB_SPEED_HIGH)
>
I tried this patch and it worked. I agree this patch is better and it
avoids introducing new locks.
Best,
Yue
next prev parent reply other threads:[~2024-04-16 9:06 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 6:52 [Linux kernel bug] general protection fault in disable_store Sam Sun
2024-04-11 6:58 ` Greg KH
2024-04-11 7:19 ` Sam Sun
2024-04-11 15:24 ` Alan Stern
2024-04-12 13:08 ` Sam Sun
2024-04-12 14:40 ` Alan Stern
2024-04-12 16:26 ` Sam Sun
2024-04-12 18:11 ` Alan Stern
2024-04-12 18:32 ` Alan Stern
2024-04-13 5:08 ` Sam Sun
2024-04-15 14:47 ` Alan Stern
2024-04-16 9:05 ` Sam Sun [this message]
2024-04-16 16:35 ` Alan Stern
2024-04-17 7:39 ` Sam Sun
2024-04-17 14:23 ` Alan Stern
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