linux-kernel - Re: [PATCH] FS: nilfs2: potential integer overflow in nilfs_ioctl_clean

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Date:	Fri, 02 Dec 2011 00:33:12 +0900 (JST)
From:	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To:	haogangchen@...il.com
Cc:	linux-nilfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] FS: nilfs2: potential integer overflow in
 nilfs_ioctl_clean_segments()

On Wed, 30 Nov 2011 21:59:59 -0500, Haogang Chen wrote:
> There is a potential integer overflow in nilfs_ioctl_clean_segments().
> When a large argv[n].v_nmembs is passed from the userspace, the
> subsequent call to vmalloc() will allocate a buffer smaller than
> expected, which leads to out-of-bound access in
> nilfs_ioctl_move_blocks() and lfs_clean_segments().
> 
> The following check does not prevent the overflow because nsegs is also
> controlled by the userspace and could be very large.
> 
> 		if (argv[n].v_nmembs > nsegs * nilfs->ns_blocks_per_segment)
> 			goto out_free;
> 
> This patch clamps argv[n].v_nmembs to UINT_MAX / argv[n].v_size, and
> returns -EINVAL when overflow.
> 
> Signed-off-by: Haogang Chen <haogangchen@...il.com>

Ahh, that makes sense.

I will apply your patch.

Thanks,
Ryusuke Konishi

> ---
>  fs/nilfs2/ioctl.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
> index 41d6743..b805df9 100644
> --- a/fs/nilfs2/ioctl.c
> +++ b/fs/nilfs2/ioctl.c
> @@ -625,6 +625,9 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
>  		if (argv[n].v_nmembs > nsegs * nilfs->ns_blocks_per_segment)
>  			goto out_free;
>  
> +		if (argv[n].v_nmembs >= UINT_MAX / argv[n].v_size)
> +			goto out_free;
> +
>  		len = argv[n].v_size * argv[n].v_nmembs;
>  		base = (void __user *)(unsigned long)argv[n].v_base;
>  		if (len == 0) {
> -- 
> 1.7.5.4
> 
> --
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