linux-kernel - Re: [PATCH 2/5 v3] Modify behaviour of request_*muxed

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>] [day] [month] [year] [list]

Message-ID: <20171218190741.GB6424@roeck-us.net>
Date:   Mon, 18 Dec 2017 11:07:41 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Zoltan Boszormenyi <zboszor@...hu>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-watchdog@...r.kernel.org, linux-i2c@...r.kernel.org,
        Paul Menzel <paulepanter@...rs.sourceforge.net>,
        Christian Fetzer <fetzer.ch@...il.com>,
        Jean Delvare <jdelvare@...e.com>,
        Nehal Shah <nehal-bakulchandra.shah@....com>,
        Tim Small <tim@...ss.co.uk>, kernel@...ss.net, wim@...ana.be,
        jlayton@...chiereds.net, marc.2377@...il.com,
        cshorler@...glemail.com, wsa@...-dreams.de,
        regressions@...mhuis.info,
        Alex Williamson <alex.williamson@...hat.com>, lyude@...hat.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Toshi Kani <toshi.kani@....com>,
        Jiang Liu <jiang.liu@...ux.intel.com>,
        Jakub Sitnicki <jsitnicki@...il.com>,
        Thierry Reding <treding@...dia.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Simon Guinot <simon.guinot@...uanux.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Mike Travis <travis@....com>,
        Daeseok Youn <daeseok.youn@...il.com>,
        Huang Rui <ray.huang@....com>, Andiry Xu <andiry.xu@....com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        David Howells <dhowells@...hat.com>,
        Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        Alexandre Desnoyers <alex@...c.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wan ZongShun <Vincent.Wan@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Lucas Stach <dev@...xeye.de>,
        Denis Turischev <denis.turischev@...pulab.co.il>
Subject: Re: [PATCH 2/5 v3] Modify behaviour of request_*muxed_region()

On Mon, Dec 18, 2017 at 09:48:38AM +0100, Zoltan Boszormenyi wrote:
> From: Böszörményi Zoltán <zboszor@...hu>
> 
> In order to make request_*muxed_region() behave more like
> mutex_lock(), a possible failure case needs to be eliminated.
> When drivers do not properly share the same I/O region, e.g.
> one is using request_region() and the other is using
> request_muxed_region(), the kernel didn't warn the user about it.
> This change modifies IORESOURCE_MUXED behaviour so it always
> goes to sleep waiting for the resuorce to be freed and the

resource

> inconsistent resource flag usage is logged with KERN_ERR.
> 
> v2: Fixed checkpatch.pl warnings and extended the comment
>     about request_declared_muxed_region.
> 
> v3: Rebased for 4.15-rc4
> 
> Signed-off-by: Zoltán Böszörményi <zboszor@...hu>
> ---
>  kernel/resource.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 05db9c4e3992..0f26f887ac33 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1143,6 +1143,7 @@ resource_size_t resource_alignment(struct resource *res)
>   *
>   * request_declared_muxed_region creates a new shared busy region
>   * described in an existing resource descriptor.
> + * It only returns if it succeeded.
>   *
>   * release_region releases a matching busy region.
>   * The region is only freed if it was allocated.
> @@ -1209,7 +1210,10 @@ struct resource *__request_declared_region(struct resource *parent,
>  				continue;
>  			}
>  		}
> -		if (conflict->flags & flags & IORESOURCE_MUXED) {
> +		if (flags & IORESOURCE_MUXED) {
> +			if (!(conflict->flags & IORESOURCE_MUXED))
> +				pr_err("Resource conflict between muxed \"%s\" and non-muxed \"%s\" I/O regions!\n",
> +					res->name, conflict->name);

With this, the muxed resource requestor will hang since the non-muxed
requestor will not release the resource. I understand that you are trying
to get rid of the error return, but is replacing it with a hang really
better ?

>  			add_wait_queue(&muxed_resource_wait, &wait);
>  			write_unlock(&resource_lock);
>  			set_current_state(TASK_UNINTERRUPTIBLE);
> -- 
> 2.13.6
>