On 11/7/2023 5:40 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the inode_post_create_tmpfile hook.
>
> As temp files can be made persistent, treat new temp files like other new
> files, so that the file hash is calculated and stored in the security
> xattr.
>
> LSMs could also take some action after temp files have been created.
>
> The new hook cannot return an error and cannot cause the operation to be
> canceled.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> ---
> fs/namei.c | 1 +
> include/linux/lsm_hook_defs.h | 2 ++
> include/linux/security.h | 6 ++++++
> security/security.c | 15 +++++++++++++++
> 4 files changed, 24 insertions(+)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index b7f433720b1e..adb3ab27951a 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3686,6 +3686,7 @@ static int vfs_tmpfile(struct mnt_idmap *idmap,
> inode->i_state |= I_LINKABLE;
> spin_unlock(&inode->i_lock);
> }
> + security_inode_post_create_tmpfile(idmap, inode);
> ima_post_create_tmpfile(idmap, inode);
> return 0;
> }
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index e491951399f7..ec5319ec2e85 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -121,6 +121,8 @@ 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 *inode)
> 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 68cbdc84506e..0c85f0337a9e 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -344,6 +344,8 @@ 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 *inode);
> 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);
> @@ -809,6 +811,10 @@ 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 *inode)
> +{ }
> +
> 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 5eaf5f2aa5ea..ca650c285fd9 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2013,6 +2013,21 @@ int security_inode_create(struct inode *dir, struct dentry *dentry,
> }
> EXPORT_SYMBOL_GPL(security_inode_create);
>
> +/**
> + * security_inode_post_create_tmpfile() - Update inode security of new tmpfile
> + * @idmap: idmap of the mount
> + * @inode: inode of the new tmpfile
> + *
> + * Update inode security data after a tmpfile has been created.
> + */
> +void security_inode_post_create_tmpfile(struct mnt_idmap *idmap,
> + struct inode *inode)
> +{
> + if (unlikely(IS_PRIVATE(inode)))
> + return;
> + call_void_hook(inode_post_create_tmpfile, idmap, inode);
> +}
> +
> /**
> * security_inode_link() - Check if creating a hard link is allowed
> * @old_dentry: existing file
