linux-kernel - Re: [PATCH 14/28] security: Introduce inode_post

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Date:   Wed, 08 Mar 2023 10:19:05 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        viro@...iv.linux.org.uk, chuck.lever@...cle.com,
        jlayton@...nel.org, 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,
        stefanb@...ux.ibm.com, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH 14/28] security: Introduce inode_post_setattr hook

Hi Roberto,

On Fri, 2023-03-03 at 19:18 +0100, 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_setattr hook.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

Other than the one minor comment below,

Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> ---
>  fs/attr.c                     |  1 +
>  include/linux/lsm_hook_defs.h |  2 ++
>  include/linux/security.h      |  7 +++++++
>  security/security.c           | 16 ++++++++++++++++
>  4 files changed, 26 insertions(+)
> 
> diff --git a/fs/attr.c b/fs/attr.c
> index da45cf01be6..343d6d62435 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -485,6 +485,7 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
>  
>  	if (!error) {
>  		fsnotify_change(dentry, ia_valid);
> +		security_inode_post_setattr(idmap, dentry, ia_valid);
>  		ima_inode_post_setattr(idmap, dentry, ia_valid);
>  		evm_inode_post_setattr(idmap, dentry, ia_valid);
>  	}
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 4372a6b2632..eedefbcdde3 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -135,6 +135,8 @@ LSM_HOOK(int, 0, inode_follow_link, struct dentry *dentry, struct inode *inode,
>  LSM_HOOK(int, 0, inode_permission, struct inode *inode, int mask)
>  LSM_HOOK(int, 0, inode_setattr, struct mnt_idmap *idmap, struct dentry *dentry,
>  	 struct iattr *attr)
> +LSM_HOOK(void, LSM_RET_VOID, inode_post_setattr, struct mnt_idmap *idmap,
> +	 struct dentry *dentry, int ia_valid)
>  LSM_HOOK(int, 0, inode_getattr, const struct path *path)
>  LSM_HOOK(int, 0, inode_setxattr, struct mnt_idmap *idmap,
>  	 struct dentry *dentry, const char *name, const void *value,
> diff --git a/include/linux/security.h b/include/linux/security.h
> index cd23221ce9e..64224216f6c 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -354,6 +354,8 @@ int security_inode_follow_link(struct dentry *dentry, struct inode *inode,
>  int security_inode_permission(struct inode *inode, int mask);
>  int security_inode_setattr(struct mnt_idmap *idmap,
>  			   struct dentry *dentry, struct iattr *attr);
> +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> +				 int ia_valid);
>  int security_inode_getattr(const struct path *path);
>  int security_inode_setxattr(struct mnt_idmap *idmap,
>  			    struct dentry *dentry, const char *name,
> @@ -855,6 +857,11 @@ static inline int security_inode_setattr(struct mnt_idmap *idmap,
>  	return 0;
>  }
>  
> +static inline void
> +security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> +			    int ia_valid)
> +{ }
> +
>  static inline int security_inode_getattr(const struct path *path)
>  {
>  	return 0;
> diff --git a/security/security.c b/security/security.c
> index f7fe252e9d3..2dbf225f5d8 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2190,6 +2190,22 @@ int security_inode_getattr(const struct path *path)
>  	return call_int_hook(inode_getattr, 0, path);
>  }
>  

Like the definitions, move the security_inode_post_setattr() to after
security_inode_setattr().

> +/**
> + * security_inode_post_setattr() - Update the inode after a setattr operation
> + * @idmap: idmap of the mount
> + * @dentry: file
> + * @ia_valid: file attributes set
> + *
> + * Update inode security field after successful setting file attributes.
> + */
> +void security_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *entry,
> +				 int ia_valid)
> +{
> +	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> +		return;
> +	call_void_hook(inode_post_setattr, idmap, dentry, ia_valid);
> +}
> +
>  /**
>   * security_inode_setxattr() - Check if setting file xattrs is allowed
>   * @idmap: idmap of the mounth

-- 
thanks,

Mimi