linux-kernel - Re: [PATCH 1/6] livepatch v5: avoid race when checking for state of the patch

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:	Tue, 9 Dec 2014 12:32:49 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Petr Mladek <pmladek@...e.cz>
Cc:	Seth Jennings <sjenning@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Miroslav Benes <mbenes@...e.cz>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Christoph Hellwig <hch@...radead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	live-patching@...r.kernel.org, x86@...nel.org, kpatch@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] livepatch v5: avoid race when checking for state of
 the patch

On Tue, Dec 09, 2014 at 07:05:02PM +0100, Petr Mladek wrote:
> klp_patch_enable() and klp_patch_disable() should check the current state
> of the patch under the klp_lock. Otherwise, it might detect that the operation
> is valid but the situation might change before it takes the lock.

Hi Petr,

Thanks for the patches.

I don't think this patch is necessary.  klp_is_enabled() doesn't check
the state of the patch.  It checks the initialization state of the core
module (klp_root_kobj), which can only be set in klp_init().  It's not
protected by the lock, so I don't see the point of this patch.

> 
> Signed-off-by: Petr Mladek <pmladek@...e.cz>
> ---
>  kernel/livepatch/core.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index d6d0f50e81f8..b848069e44cc 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -425,11 +425,13 @@ int klp_disable_patch(struct klp_patch *patch)
>  {
>  	int ret;
>  
> -	if (!klp_is_enabled())
> -		return -ENODEV;
> -
>  	mutex_lock(&klp_mutex);
>  
> +	if (!klp_is_enabled()) {
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
>  	if (!klp_patch_is_registered(patch)) {
>  		ret = -EINVAL;
>  		goto err;
> @@ -489,11 +491,13 @@ int klp_enable_patch(struct klp_patch *patch)
>  {
>  	int ret;
>  
> -	if (!klp_is_enabled())
> -		return -ENODEV;
> -
>  	mutex_lock(&klp_mutex);
>  
> +	if (!klp_is_enabled()) {
> +		ret = -ENODEV;
> +		goto err;
> +	}
> +
>  	if (!klp_patch_is_registered(patch)) {
>  		ret = -EINVAL;
>  		goto err;
> -- 
> 1.8.5.2
> 

-- 
Josh
--
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/