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

Paul Moore
2024-07-19T02:08:05Z

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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