linux-kernel - Re: [PATCH] fs:Fix kmemleak leak warning in getname_flags about working on unitialized memory

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Message-ID: <df8dd6cd-245d-0673-0246-e514b2a67fc2@I-love.SAKURA.ne.jp>
Date:	Thu, 4 Aug 2016 21:18:19 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	Nicholas Krause <xerofoify@...il.com>, viro@...iv.linux.org.uk
Cc:	akpm@...ux-foundation.org, msalter@...hat.com,
	kuleshovmail@...il.com, david.vrabel@...rix.com, vbabka@...e.cz,
	ard.biesheuvel@...aro.org, jgross@...e.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] fs:Fix kmemleak leak warning in getname_flags about
 working on unitialized memory

On 2016/08/04 6:48, Nicholas Krause wrote:
> This fixes a kmemleak leak warning complaining about working on
> unitializied memory as found in the function, getname_flages. Seems
> that we are indeed working on unitialized memory, as the filename
> char pointer is never made to point to the filname structure's result
> member for holding it's name, fix this by using memcpy to copy the
> filname structure pointer's, name to the char pointer passed to this
> function.
> 
> Signed-off-by: Nicholas Krause <xerofoify@...il.com>
> ---
>  fs/namei.c         | 1 +
>  mm/early_ioremap.c | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index c386a32..6b18d57 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -196,6 +196,7 @@ getname_flags(const char __user *filename, int flags, int *empty)
>  		}
>  	}
>  
> +	memcpy((char *)result->name, filename, len);

This filename is a __user pointer. Reading with memcpy() is not safe.

>  	result->uptr = filename;
>  	result->aname = NULL;
>  	audit_getname(result);