linux-kernel - Re: [PATCH] kernel/resource.c: fix stack overflow in __reserve_region_with

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 28 Aug 2012 12:30:08 +0800
From:	Ram Pai <linuxram@...ibm.com>
To:	T Makphaibulchoke <tmac@...com>
Cc:	akpm@...ux-foundation.org, paul.gortmaker@...driver.com,
	weiyang@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/resource.c: fix stack overflow in
 __reserve_region_with_split

On Mon, Aug 27, 2012 at 06:47:54PM -0600, T Makphaibulchoke wrote:
> Using recurvise call to try adding a non-conflicting region in the function
> __reserve_region_with_split() could result in a stack overflow in the case
> that the recursive calls are too deep.  Convert the recursive calls to
> an iterative loop to avoid the problem.
> 
> Signed-off-by: T Makphaibulchoke <tmac@...com>
> ---
>  kernel/resource.c |   32 ++++++++++++++++++--------------
>  1 files changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 34d4588..d6e9f9c 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -768,25 +768,29 @@ static void __init __reserve_region_with_split(struct resource *root,
>  		return;
> 
>  	res->name = name;
> -	res->start = start;
> -	res->end = end;
>  	res->flags = IORESOURCE_BUSY;
> 
> -	conflict = __request_resource(parent, res);
> -	if (!conflict)
> -		return;
> +	while (1) {
> +		res->start = start;
> +		res->end = end;
> 
> -	/* failed, split and try again */
> -	kfree(res);
> +		conflict = __request_resource(parent, res);
> +		if (!conflict)
> +			break;
> 
> -	/* conflict covered whole area */
> -	if (conflict->start <= start && conflict->end >= end)
> -		return;
> +		/* conflict covered whole area */
> +		if (conflict->start <= start && conflict->end >= end) {
> +			kfree(res);
> +			break;
> +		}
> +
> +		/* failed, split and try again */
> +		if (conflict->start > start)
> +			end = conflict->start - 1;
> +		if (conflict->end < end)
> +			start = conflict->end + 1;
> +	}

Earlier the patch reserved all areas from 'start' to 'end' skipping any
conflicting intermediate regions.  Your patch will reserve just the
first available fragment before the conflicting range, but will not 
reserve any fragments after the conflicting range. 

For example:
if the region requested is 1 to 100, but 20-30 is already reserved, than
the earlier behavior would reserve 1-20 and 30-100. With your
patch, it will just reserve 1-20.

RP

--
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/