netdev - Re: [PATCH net-next v2 2/3] r8152: clear the flag of SCHEDULE

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: <20141031.161520.3547230591227504.davem@davemloft.net>
Date:	Fri, 31 Oct 2014 16:15:20 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	hayeswang@...ltek.com
Cc:	netdev@...r.kernel.org, nic_swsd@...ltek.com,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/3] r8152: clear the flag of
 SCHEDULE_TASKLET in tasklet

From: Hayes Wang <hayeswang@...ltek.com>
Date: Fri, 31 Oct 2014 17:56:41 +0800

> Clear the flag of SCHEDULE_TASKLET in bottom_half() to avoid
> re-schedule the tasklet again by workqueue.
> 
> Signed-off-by: Hayes Wang <hayeswang@...ltek.com>
> ---
>  drivers/net/usb/r8152.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index ff54098..670279a 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -1798,6 +1798,9 @@ static void bottom_half(unsigned long data)
>  	if (!netif_carrier_ok(tp->netdev))
>  		return;
>  
> +	if (test_bit(SCHEDULE_TASKLET, &tp->flags))
> +		clear_bit(SCHEDULE_TASKLET, &tp->flags);

This is racey.

If another thread of control sets the bit between the test and the
clear, you will lose an event.

It really never makes sense to work with atomic bitops in a non-atomic
test-and-whatever manner like this, it's always a red flag and
indicates you're doing something very wrong.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html