linux-kernel - Re: [PATCH] eCryptfs: check readlink result was not an error before using it

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Message-ID: <20081211193228.GA13627@halcrowt61p.lan>
Date:	Thu, 11 Dec 2008 13:32:28 -0600
From:	Michael Halcrow <mhalcrow@...ibm.com>
To:	Duane Griffin <duaneg@...da.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Boaz Harrosh <bharrosh@...asas.com>,
	Mike.Halcrow.mhalcrow@...ibm.com,
	Phillip.Hellewell.phillip@...lewell.homeip.net,
	ecryptfs-devel@...ts.sourceforge.net
Subject: Re: [PATCH] eCryptfs: check readlink result was not an error
	before using it

On Thu, Dec 11, 2008 at 07:16:26PM +0000, Duane Griffin wrote:
> The result from readlink is being used to index into the link name
> buffer without checking whether it is a valid length. If readlink
> returns an error this will fault or cause memory corruption.
> 
> Signed-off-by: Duane Griffin <duaneg@...da.com>

Acked-by: Michael Halcrow <mhalcrow@...ibm.com>

> ---
>  fs/ecryptfs/inode.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
> index 89209f0..5e78fc1 100644
> --- a/fs/ecryptfs/inode.c
> +++ b/fs/ecryptfs/inode.c
> @@ -673,10 +673,11 @@ static void *ecryptfs_follow_link(struct dentry *dentry, struct nameidata *nd)
>  	ecryptfs_printk(KERN_DEBUG, "Calling readlink w/ "
>  			"dentry->d_name.name = [%s]\n", dentry->d_name.name);
>  	rc = dentry->d_inode->i_op->readlink(dentry, (char __user *)buf, len);
> -	buf[rc] = '\0';
>  	set_fs(old_fs);
>  	if (rc < 0)
>  		goto out_free;
> +	else
> +		buf[rc] = '\0';
>  	rc = 0;
>  	nd_set_link(nd, buf);
>  	goto out;
--
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