Re: [PATCH v4 5/20] lsm: Refactor return value of LSM hook inode_copy_up_xattr

[Paul Moore <paul@paul-moore.com>]

On Jul 11, 2024 Xu Kuohai <xukuohai@huaweicloud.com> wrote:
> 
> To be consistent with most LSM hooks, convert the return value of
> hook inode_copy_up_xattr to 0 or a negative error code.
> 
> Before:
> - Hook inode_copy_up_xattr returns 0 when accepting xattr, 1 when
>   discarding xattr, -EOPNOTSUPP if it does not know xattr, or any
>   other negative error code otherwise.
> 
> After:
> - Hook inode_copy_up_xattr returns 0 when accepting xattr, *-ECANCELED*
>   when discarding xattr, -EOPNOTSUPP if it does not know xattr, or
>   any other negative error code otherwise.
> 
> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
> ---
>  fs/overlayfs/copy_up.c            |  6 +++---
>  security/integrity/evm/evm_main.c |  2 +-
>  security/security.c               | 12 ++++++------
>  security/selinux/hooks.c          |  4 ++--
>  security/smack/smack_lsm.c        |  6 +++---
>  5 files changed, 15 insertions(+), 15 deletions(-)

...

> diff --git a/security/security.c b/security/security.c
> index 26eea8f4cd74..12215ca286af 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2675,18 +2675,18 @@ EXPORT_SYMBOL(security_inode_copy_up);
>   * lower layer to the union/overlay layer.   The caller is responsible for
>   * reading and writing the xattrs, this hook is merely a filter.
>   *
> - * Return: Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP
> - *         if the security module does not know about attribute, or a negative
> - *         error code to abort the copy up.
> + * Return: Returns 0 to accept the xattr, -ECANCELED to discard the xattr,
> + *         -EOPNOTSUPP if the security module does not know about attribute,
> + *         or a negative error code to abort the copy up.
>   */
>  int security_inode_copy_up_xattr(struct dentry *src, const char *name)
>  {
>  	int rc;
>  
>  	/*
> -	 * The implementation can return 0 (accept the xattr), 1 (discard the
> -	 * xattr), -EOPNOTSUPP if it does not know anything about the xattr or
> -	 * any other error code in case of an error.
> +	 * The implementation can return 0 (accept the xattr), -ECANCELED
> +	 * (discard the xattr), -EOPNOTSUPP if it does not know anything
> +	 *  about the xattr or any other error code in case of an error.
>  	 */

Updating the comment here is good, but considering that we also discuss
the return value in the function header comment, I think it might be
better to just remove this comment entirely and leave the function header
comment as the single source.  Duplicated comments/docs tend to fall out
of sync and create confusion.

>  	rc = call_int_hook(inode_copy_up_xattr, src, name);
>  	if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))


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