[PATCH v4 1/3] lsm: introduce new hooks for setting/getting inode fsxattr

[Mickaël Salaün]

On Fri, Mar 21, 2025 at 08:48:40PM +0100, Andrey Albershteyn wrote:
> Introduce new hooks for setting and getting filesystem extended
> attributes on inode (FS_IOC_FSGETXATTR).
> 
> Cc: selinux at vger.kernel.org
> Cc: Paul Moore <paul at paul-moore.com>
> 
> Signed-off-by: Andrey Albershteyn <aalbersh at kernel.org>
> ---
>  fs/ioctl.c                    |  7 ++++++-
>  include/linux/lsm_hook_defs.h |  4 ++++
>  include/linux/security.h      | 16 ++++++++++++++++
>  security/security.c           | 32 ++++++++++++++++++++++++++++++++
>  4 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 638a36be31c14afc66a7fd6eb237d9545e8ad997..4434c97bc5dff5a3e8635e28745cd99404ff353e 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -525,10 +525,15 @@ EXPORT_SYMBOL(fileattr_fill_flags);
>  int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
>  {
>  	struct inode *inode = d_inode(dentry);
> +	int error;
>  
>  	if (!inode->i_op->fileattr_get)
>  		return -ENOIOCTLCMD;
>  
> +	error = security_inode_getfsxattr(inode, fa);

It would help for both of these hooks to pass the dentry instead of the
inode.

> +	if (error)
> +		return error;
> +
>  	return inode->i_op->fileattr_get(dentry, fa);
>  }
>  EXPORT_SYMBOL(vfs_fileattr_get);
> @@ -692,7 +697,7 @@ int vfs_fileattr_set(struct mnt_idmap *idmap, struct dentry *dentry,
>  			fa->flags |= old_ma.flags & ~FS_COMMON_FL;
>  		}
>  		err = fileattr_set_prepare(inode, &old_ma, fa);
> -		if (!err)
> +		if (!err && !security_inode_setfsxattr(inode, fa))
>  			err = inode->i_op->fileattr_set(idmap, dentry, fa);
>  	}
>  	inode_unlock(inode);