Re: [PATCH 2/9] selinux: Implementation for inode_copy_up() hook

[Stephen Smalley]

On 07/13/2016 10:44 AM, Vivek Goyal wrote:
> A file is being copied up for overlay file system. Prepare a new set of
> creds and set create_sid appropriately so that new file is created with
> appropriate label.
> 
> Overlay inode has right label for both context and non-context mount
> cases. In case of non-context mount, overlay inode will have the label
> of lower file and in case of context mount, overlay inode will have
> the label from context= mount option.
> 
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>

Acked-by: Stephen Smalley <sds@xxxxxxxxxxxxx>

> ---
>  security/selinux/hooks.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a86d537..c82ee54 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3270,6 +3270,26 @@ static void selinux_inode_getsecid(struct inode *inode, u32 *secid)
>  	*secid = isec->sid;
>  }
>  
> +static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
> +{
> +	u32 sid;
> +	struct task_security_struct *tsec;
> +	struct cred *new_creds = *new;
> +
> +	if (new_creds == NULL) {
> +		new_creds = prepare_creds();
> +		if (!new_creds)
> +			return -ENOMEM;
> +	}
> +
> +	tsec = new_creds->security;
> +	/* Get label from overlay inode and set it in create_sid */
> +	selinux_inode_getsecid(d_inode(src), &sid);
> +	tsec->create_sid = sid;
> +	*new = new_creds;
> +	return 0;
> +}
> +
>  /* file security operations */
>  
>  static int selinux_revalidate_file_permission(struct file *file, int mask)
> @@ -6056,6 +6076,7 @@ static struct security_hook_list selinux_hooks[] = {
>  	LSM_HOOK_INIT(inode_setsecurity, selinux_inode_setsecurity),
>  	LSM_HOOK_INIT(inode_listsecurity, selinux_inode_listsecurity),
>  	LSM_HOOK_INIT(inode_getsecid, selinux_inode_getsecid),
> +	LSM_HOOK_INIT(inode_copy_up, selinux_inode_copy_up),
>  
>  	LSM_HOOK_INIT(file_permission, selinux_file_permission),
>  	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
>