On Wed, Nov 29, 2023 at 11:50 PM Seth Forshee (DigitalOcean)
<sforshee@xxxxxxxxxx> wrote:
>
> Provide a type-safe interface for setting filesystem capabilities and a
> generic implementation suitable for most filesystems.
>
> Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx>
> ---
> fs/xattr.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 2 ++
> 2 files changed, 89 insertions(+)
>
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 3abaf9bef0a5..03cc824e4f87 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -247,6 +247,93 @@ int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
> }
> EXPORT_SYMBOL(vfs_get_fscaps);
>
> +static int generic_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
> + const struct vfs_caps *caps, int flags)
> +{
> + struct inode *inode = d_inode(dentry);
> + struct vfs_ns_cap_data nscaps;
> + int size;
> +
> + size = vfs_caps_to_xattr(idmap, i_user_ns(inode), caps,
> + &nscaps, sizeof(nscaps));
> + if (size < 0)
> + return size;
> +
> + return __vfs_setxattr_noperm(idmap, dentry, XATTR_NAME_CAPS,
> + &nscaps, size, flags);
> +}
> +
> +/**
> + * vfs_set_fscaps - set filesystem capabilities
> + * @idmap: idmap of the mount the inode was found from
> + * @dentry: the dentry on which to set filesystem capabilities
> + * @caps: the filesystem capabilities to be written
> + * @flags: setxattr flags to use when writing the capabilities xattr
> + *
> + * This function writes the supplied filesystem capabilities to the dentry.
> + *
> + * Return: 0 on success, a negative errno on error.
> + */
> +int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry,
> + const struct vfs_caps *caps, int flags)
> +{
> + struct inode *inode = d_inode(dentry);
> + struct inode *delegated_inode = NULL;
> + struct vfs_ns_cap_data nscaps;
> + int size, error;
> +
> + /*
> + * Unfortunately EVM wants to have the raw xattr value to compare to
> + * the on-disk version, so we need to pass the raw xattr to the
> + * security hooks. But we also want to do security checks before
> + * breaking leases, so that means a conversion to the raw xattr here
> + * which will usually be reduntant with the conversion we do for
> + * writing the xattr to disk.
> + */
> + size = vfs_caps_to_xattr(idmap, i_user_ns(inode), caps, &nscaps,
> + sizeof(nscaps));
> + if (size < 0)
> + return size;
> +
> +retry_deleg:
> + inode_lock(inode);
> +
> + error = xattr_permission(idmap, inode, XATTR_NAME_CAPS, MAY_WRITE);
> + if (error)
> + goto out_inode_unlock;
> + error = security_inode_setxattr(idmap, dentry, XATTR_NAME_CAPS, &nscaps,
> + size, flags);
> + if (error)
> + goto out_inode_unlock;
> +
> + error = try_break_deleg(inode, &delegated_inode);
> + if (error)
> + goto out_inode_unlock;
> +
> + if (inode->i_opflags & IOP_XATTR) {
> + if (inode->i_op->set_fscaps)
> + error = inode->i_op->set_fscaps(idmap, dentry, caps, flags);
> + else
> + error = generic_set_fscaps(idmap, dentry, caps, flags);
I think the non-generic case is missing fsnotify_xattr().
See vfs_set_acl() for comparison.
Thanks,
Amir.
