linux-kernel - Re: [PATCH] Mailbox: Complete wait event only if Tx was successful

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]

Date:	Fri, 12 Dec 2014 15:51:54 +0530
From:	Jassi Brar <jaswinder.singh@...aro.org>
To:	Ashwin Chaugule <ashwin.chaugule@...aro.org>
Cc:	Mark Brown <broonie@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] Mailbox: Complete wait event only if Tx was successful

On 11 December 2014 at 01:46, Ashwin Chaugule
<ashwin.chaugule@...aro.org> wrote:
> If a wait_for_completion_timeout() call returns due to a timeout,
> the mbox code can still call complete() after returning from the wait.
> This can cause subsequent transmissions on a channel to fail, since
> the wait_for_completion_timeout() sees the completion variable
> is !=0, caused by the erroneous complete() call, and immediately
> returns without waiting for the time as expected by the client.
>
> Fix this by calling complete() only if the TX was successful.
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@...aro.org>
> ---
>  drivers/mailbox/mailbox.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> index 17e9e4a..4acaddb 100644
> --- a/drivers/mailbox/mailbox.c
> +++ b/drivers/mailbox/mailbox.c
> @@ -101,7 +101,7 @@ static void tx_tick(struct mbox_chan *chan, int r)
>         if (mssg && chan->cl->tx_done)
>                 chan->cl->tx_done(chan->cl, mssg, r);
>
> -       if (chan->cl->tx_block)
> +       if ((!r) && chan->cl->tx_block)
>                 complete(&chan->tx_complete);
>
Thanks for finding the bug.
However the fix is flawed. complete() could also be done from
mbox_chan_txdone() calling tx_tick(). And if the controller returned
error, we could never pass on that error code to the user (timeout
fires and then we will move on with -EIO).
Since we could never prevent the controller from returning -EIO as the
error, I think we have to explicitly tell tx_tick() if it needs to
complete() or not.

-Jassi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/