linux-kernel - Re: [PATCH] ovl: filter of trusted xattr results in audit

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Date:   Mon, 7 Oct 2019 18:16:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        linux-security-module@...r.kernel.org, stable@...r.kernel.org,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-unionfs@...r.kernel.org
Subject: Re: [PATCH] ovl: filter of trusted xattr results in audit

On Mon, Oct 07, 2019 at 09:09:16AM -0700, Mark Salyzyn wrote:
> When filtering xattr list for reading, presence of trusted xattr
> results in a security audit log.  However, if there is other content
> no errno will be set, and if there isn't, the errno will be -ENODATA
> and not -EPERM as is usually associated with a lack of capability.
> The check does not block the request to list the xattrs present.
> 
> Switch to has_capability_noaudit to reflect a more appropriate check.
> 
> Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
> Cc: linux-security-module@...r.kernel.org
> Cc: kernel-team@...roid.com
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: stable@...r.kernel.org # v3.18
> Fixes: upstream a082c6f680da ("ovl: filter trusted xattr for non-admin")
> Fixes: 3.18 4bcc9b4b3a0a ("ovl: filter trusted xattr for non-admin")
> ---
> Replaced ns_capable_noaudit with 3.18.y tree specific
> has_capability_noaudit present in original submission to kernel.org
> commit 5c2e9f346b815841f9bed6029ebcb06415caf640
> ("ovl: filter of trusted xattr results in audit")
> 
>  fs/overlayfs/inode.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index a01ec1836a72..1175efa5e956 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -265,7 +265,8 @@ static bool ovl_can_list(const char *s)
>  		return true;
>  
>  	/* Never list trusted.overlay, list other trusted for superuser only */
> -	return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
> +	return !ovl_is_private_xattr(s) &&
> +	       has_capability_noaudit(current, CAP_SYS_ADMIN);
>  }
>  
>  ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
> -- 
> 2.23.0.581.g78d2f28ef7-goog
> 

Thanks for the backport, this one worked!

greg k-h