linux-kernel - Re: [PATCH 19/28] security: Introduce inode_post_create

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Date:   Mon, 6 Mar 2023 14:35:37 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        viro@...iv.linux.org.uk, chuck.lever@...cle.com,
        jlayton@...nel.org, zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
        paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com,
        dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        casey@...aufler-ca.com, brauner@...nel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        selinux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH 19/28] security: Introduce inode_post_create_tmpfile hook



On 3/3/23 13:18, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
> 
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_create_tmpfile hook.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
>   fs/namei.c                    |  1 +
>   include/linux/lsm_hook_defs.h |  2 ++
>   include/linux/security.h      |  8 ++++++++
>   security/security.c           | 18 ++++++++++++++++++
>   4 files changed, 29 insertions(+)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 3f2747521d3..8c4fdfd81d4 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3624,6 +3624,7 @@ static int vfs_tmpfile(struct mnt_idmap *idmap,
>   		inode->i_state |= I_LINKABLE;
>   		spin_unlock(&inode->i_lock);
>   	}
> +	security_inode_post_create_tmpfile(idmap, dir, file_dentry(file), mode);
>   	ima_post_create_tmpfile(idmap, dir, file_dentry(file), mode);
>   	return 0;
>   }
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 32c801a3ea2..5dc2a7c3d9a 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -120,6 +120,8 @@ LSM_HOOK(int, 0, inode_init_security_anon, struct inode *inode,
>   	 const struct qstr *name, const struct inode *context_inode)
>   LSM_HOOK(int, 0, inode_create, struct inode *dir, struct dentry *dentry,
>   	 umode_t mode)
> +LSM_HOOK(void, LSM_RET_VOID, inode_post_create_tmpfile, struct mnt_idmap *idmap,
> +	 struct inode *dir, struct dentry *dentry, umode_t mode)
>   LSM_HOOK(int, 0, inode_link, struct dentry *old_dentry, struct inode *dir,
>   	 struct dentry *new_dentry)
>   LSM_HOOK(int, 0, inode_unlink, struct inode *dir, struct dentry *dentry)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index fb6e9d434c6..b3e201404dc 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -337,6 +337,9 @@ int security_inode_init_security_anon(struct inode *inode,
>   				      const struct qstr *name,
>   				      const struct inode *context_inode);
>   int security_inode_create(struct inode *dir, struct dentry *dentry, umode_t mode);
> +void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
> +					struct inode *dir,
> +					struct dentry *dentry, umode_t mode);
>   int security_inode_link(struct dentry *old_dentry, struct inode *dir,
>   			 struct dentry *new_dentry);
>   int security_inode_unlink(struct inode *dir, struct dentry *dentry);
> @@ -787,6 +790,11 @@ static inline int security_inode_create(struct inode *dir,
>   	return 0;
>   }
>   
> +static inline void
> +security_inode_post_create_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
> +				   struct dentry *dentry, umode_t mode)
> +{ }
> +
>   static inline int security_inode_link(struct dentry *old_dentry,
>   				       struct inode *dir,
>   				       struct dentry *new_dentry)
> diff --git a/security/security.c b/security/security.c
> index f5f367e2064..8883082b686 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1971,6 +1971,24 @@ int security_inode_create(struct inode *dir, struct dentry *dentry,
>   }
>   EXPORT_SYMBOL_GPL(security_inode_create);
>   
> +/**
> + * security_inode_post_create_tmpfile() - Update inode sec after tmpfile created

'sec'? -> Update inode security field after creation of tmpfile



> + * @idmap: idmap of the mount
> + * @dir: the inode of the base directory
> + * @dentry: the dentry of the new tmpfile
> + * @mode: the mode of the new tmpfile
> + *
> + * Update inode security field after a tmpfile has been created.

With the nit above:

Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>


> + */
> +void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
> +					struct inode *dir,
> +					struct dentry *dentry, umode_t mode)
> +{
> +	if (unlikely(IS_PRIVATE(dir)))
> +		return;
> +	call_void_hook(inode_post_create_tmpfile, idmap, dir, dentry, mode);
> +}
> +
>   /**
>    * security_inode_link() - Check if creating a hard link is allowed
>    * @old_dentry: existing file