Re: [PATCH] fs: hardlink creation restrictions

[Marcin Slusarz]

On Sat, Feb 18, 2012 at 11:38:57AM -0800, Kees Cook wrote:
> @@ -3052,6 +3119,9 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
>  	error = mnt_want_write(new_path.mnt);
>  	if (error)
>  		goto out_dput;
> +	error = may_linkat(&old_path);
> +	if (error)
> +		goto out_dput;
>  	error = security_path_link(old_path.dentry, &new_path, new_dentry);
>  	if (error)
>  		goto out_drop_write;

You should give up write access after check failure (i.e. goto out_drop_write).

Marcin
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