linux-kernel - Re: [PATCH RFC v10 6/17] security: add new securityfs delete function

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Message-ID: <2edaa73fc9457f4a051115863d94b4ff.paul@paul-moore.com>
Date:   Sat, 08 Jul 2023 01:36:58 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Fan Wu <wufan@...ux.microsoft.com>, corbet@....net,
        zohar@...ux.ibm.com, jmorris@...ei.org, serge@...lyn.com,
        tytso@....edu, ebiggers@...nel.org, axboe@...nel.dk,
        agk@...hat.com, snitzer@...nel.org, eparis@...hat.com
Cc:     linux-doc@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
        dm-devel@...hat.com, audit@...r.kernel.org,
        roberto.sassu@...wei.com, linux-kernel@...r.kernel.org,
        Fan Wu <wufan@...ux.microsoft.com>
Subject: Re: [PATCH RFC v10 6/17] security: add new securityfs delete function

On Jun 28, 2023 Fan Wu <wufan@...ux.microsoft.com> wrote:
> 
> When deleting a directory in the security file system, the existing
> securityfs_remove requires the directory to be empty, otherwise
> it will do nothing. This leads to a potential risk that the security
> file system might be in an unclean state when the intentded deletion
> did not happen.
> 
> This commit introduces a new function securityfs_recursive_remove
> to recursively delete a directory without leaving an unclean state.
> 
> Co-developed-by: "Christian Brauner (Microsoft)" <brauner@...nel.org>
> Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>
> ---
>  include/linux/security.h |  1 +
>  security/inode.c         | 25 +++++++++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/include/linux/security.h b/include/linux/security.h
> index e2734e9e44d5..a88076ebc7b1 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1971,6 +1971,7 @@ struct dentry *securityfs_create_symlink(const char *name,
>  					 const char *target,
>  					 const struct inode_operations *iops);
>  extern void securityfs_remove(struct dentry *dentry);
> +extern void securityfs_recursive_remove(struct dentry *dentry);
>  
>  #else /* CONFIG_SECURITYFS */
>  
> diff --git a/security/inode.c b/security/inode.c
> index 6c326939750d..13358e8547e8 100644
> --- a/security/inode.c
> +++ b/security/inode.c
> @@ -313,6 +313,31 @@ void securityfs_remove(struct dentry *dentry)
>  }
>  EXPORT_SYMBOL_GPL(securityfs_remove);
>  
> +static void remove_one(struct dentry *victim)
> +{
> +	simple_release_fs(&mount, &mount_count);
> +}
> +
> +/**
> + * securityfs_recursive_remove - recursively removes a file or directory from the securityfs filesystem

I really want to see lines less than or equal to 80 characters; I
would suggest this:

"securityfs_recursive_remove - recursively removes a file or directory"

> + * @dentry: a pointer to a the dentry of the file or directory to be removed.
> + *
> + * This function recursively removes a file or directory in securityfs that was
> + * previously created with a call to another securityfs function (like
> + * securityfs_create_file() or variants thereof.)
> + */
> +void securityfs_recursive_remove(struct dentry *dentry)
> +{
> +	if (IS_ERR_OR_NULL(dentry))
> +		return;
> +
> +	simple_pin_fs(&fs_type, &mount, &mount_count);
> +	simple_recursive_removal(dentry, remove_one);
> +	simple_release_fs(&mount, &mount_count);
> +}
> +EXPORT_SYMBOL_GPL(securityfs_recursive_remove);
> +
>  #ifdef CONFIG_SECURITY
>  static struct dentry *lsm_dentry;
>  static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
> -- 
> 2.25.1

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