linux-kernel - Re: [patch] x86, pat: freeing invalid memtype messages

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Date:	Thu, 17 Jun 2010 18:17:28 +0200
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	Dan Carpenter <error27@...il.com>,
	Xiaotian Feng <dfeng@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Jack Steiner <steiner@....com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [patch] x86, pat: freeing invalid memtype messages

On Thu, Jun 17, 2010 at 03:45:59PM +0200, Dan Carpenter wrote:
> Commit 20413f27163 "x86, pat: Fix memory leak in free_memtype" added an
> error message in free_memtype() if rbt_memtype_erase() returns NULL.  
> The problem is that if CONFIG_X86_PAT is enabled, we use a different
> implimentation of rbt_memtype_erase() that always returns NULL.
> 
> I've modified rbt_memtype_erase() to return an ERR_PTR() on errors and 
> made free_memtype() check for that instead.
> 
> Addresses:  https://bugzilla.kernel.org/show_bug.cgi?id=16205
> 
> Signed-off-by: Dan Carpenter <error27@...il.com>

This patch is probably ok, but it does not address my bug.
I have CONFIG_X86_PAT=y, so rbt_memtype_erase does not always return NULL.
 
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index acc15b2..81b7735 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -359,10 +359,10 @@ int free_memtype(u64 start, u64 end)
>  	entry = rbt_memtype_erase(start, end);
>  	spin_unlock(&memtype_lock);
>  
> -	if (!entry) {
> +	if (IS_ERR(entry)) {
>  		printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
>  			current->comm, current->pid, start, end);
> -		return -EINVAL;
> +		return PTR_ERR(entry);
>  	}
>  
>  	kfree(entry);
> diff --git a/arch/x86/mm/pat_rbtree.c b/arch/x86/mm/pat_rbtree.c
> index f537087..90e5cbe 100644
> --- a/arch/x86/mm/pat_rbtree.c
> +++ b/arch/x86/mm/pat_rbtree.c
> @@ -236,8 +236,10 @@ struct memtype *rbt_memtype_erase(u64 start, u64 end)
>  	struct memtype *data;
>  
>  	data = memtype_rb_exact_match(&memtype_rbroot, start, end);
> -	if (!data)
> +	if (!data) {
> +		data = ERR_PTR(-EINVAL);
>  		goto out;
> +	}
>  
>  	rb_erase(&data->rb, &memtype_rbroot);
>  out:
> 
> 
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