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Message-ID: <CAMj1kXHkrRvUbzdNg7WGmBPFW8MtnhEsSy1FOk4GZzVZ1H4fTw@mail.gmail.com>
Date: Wed, 23 Aug 2023 18:30:12 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Jiao Zhou <jiaozhou@...gle.com>,
Matthew Garrett <mjg59@...f.ucam.org>,
Peter Jones <pjones@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, Jeremy Kerr <jk@...abs.org>,
linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel: Add Mount Option For Efivarfs
(cc Peter and Matthew)
On Tue, 22 Aug 2023 at 18:24, Jiao Zhou <jiaozhou@...gle.com> wrote:
>
> Add uid and gid in efivarfs's mount option, so that
> we can mount the file system with ownership. This approach
> is used by a number of other filesystems that don't have
> native support for ownership
>
> Signed-off-by: Jiao Zhou <jiaozhou@...gle.com>
> ---
>
> fs/efivarfs/inode.c | 4 ++++
> fs/efivarfs/internal.h | 9 +++++++
> fs/efivarfs/super.c | 54 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 67 insertions(+)
>
> diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
> index b973a2c03dde..86175e229b0f 100644
> --- a/fs/efivarfs/inode.c
> +++ b/fs/efivarfs/inode.c
> @@ -20,9 +20,13 @@ struct inode *efivarfs_get_inode(struct super_block *sb,
> const struct inode *dir, int mode,
> dev_t dev, bool is_removable)
> {
> + struct efivarfs_fs_info *fsi = sb->s_fs_info;
> struct inode *inode = new_inode(sb);
> + struct efivarfs_mount_opts *opts = &fsi->mount_opts;
>
> if (inode) {
> + inode->i_uid = opts->uid;
> + inode->i_gid = opts->gid;
> inode->i_ino = get_next_ino();
> inode->i_mode = mode;
> inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
> diff --git a/fs/efivarfs/internal.h b/fs/efivarfs/internal.h
> index 8ebf3a6a8aa2..2c7b6b24df19 100644
> --- a/fs/efivarfs/internal.h
> +++ b/fs/efivarfs/internal.h
> @@ -48,6 +48,15 @@ bool efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
> bool efivar_variable_is_removable(efi_guid_t vendor, const char *name,
> size_t len);
>
> +struct efivarfs_mount_opts {
> + kuid_t uid;
> + kgid_t gid;
> +};
> +
> +struct efivarfs_fs_info {
> + struct efivarfs_mount_opts mount_opts;
> +};
> +
> extern const struct file_operations efivarfs_file_operations;
> extern const struct inode_operations efivarfs_dir_inode_operations;
> extern bool efivarfs_valid_name(const char *str, int len);
> diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> index e028fafa04f3..e3c81fac8208 100644
> --- a/fs/efivarfs/super.c
> +++ b/fs/efivarfs/super.c
> @@ -8,6 +8,7 @@
> #include <linux/efi.h>
> #include <linux/fs.h>
> #include <linux/fs_context.h>
> +#include <linux/fs_parser.h>
> #include <linux/module.h>
> #include <linux/pagemap.h>
> #include <linux/ucs2_string.h>
> @@ -60,10 +61,27 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>
> return 0;
> }
> +static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
> +{
> + struct super_block *sb = root->d_sb;
> + struct efivarfs_fs_info *sbi = sb->s_fs_info;
> + struct efivarfs_mount_opts *opts = &sbi->mount_opts;
> +
> + /* Show partition info */
> + if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
> + seq_printf(m, ",uid=%u",
> + from_kuid_munged(&init_user_ns, opts->uid));
> + if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
> + seq_printf(m, ",gid=%u",
> + from_kgid_munged(&init_user_ns, opts->gid));
> + return 0;
> +}
> +
> static const struct super_operations efivarfs_ops = {
> .statfs = efivarfs_statfs,
> .drop_inode = generic_delete_inode,
> .evict_inode = efivarfs_evict_inode,
> + .show_options = efivarfs_show_options,
> };
>
> /*
> @@ -225,6 +243,40 @@ static int efivarfs_destroy(struct efivar_entry *entry, void *data)
> return 0;
> }
>
> +enum {
> + Opt_uid, Opt_gid,
> +};
> +
> +static const struct fs_parameter_spec efivarfs_parameters[] = {
> + fsparam_u32("uid", Opt_uid),
> + fsparam_u32("gid", Opt_gid),
> +};
> +
> +static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
> +{
> + struct efivarfs_fs_info *sbi = fc->s_fs_info;
> + struct efivarfs_mount_opts *opts = &sbi->mount_opts;
> + struct fs_parse_result result;
> + int opt;
> +
> + opt = fs_parse(fc, efivarfs_parameters, param, &result);
> + if (opt < 0)
> + return opt;
> +
> + switch (opt) {
> + case Opt_uid:
> + opts->uid = make_kuid(current_user_ns(), result.uint_32);
> + break;
> + case Opt_gid:
> + opts->gid = make_kgid(current_user_ns(), result.uint_32);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
> {
> struct inode *inode = NULL;
> @@ -271,6 +323,7 @@ static int efivarfs_get_tree(struct fs_context *fc)
>
> static const struct fs_context_operations efivarfs_context_ops = {
> .get_tree = efivarfs_get_tree,
> + .parse_param = efivarfs_parse_param,
> };
>
> static int efivarfs_init_fs_context(struct fs_context *fc)
> @@ -295,6 +348,7 @@ static struct file_system_type efivarfs_type = {
> .name = "efivarfs",
> .init_fs_context = efivarfs_init_fs_context,
> .kill_sb = efivarfs_kill_sb,
> + .parameters = efivarfs_parameters,
> };
>
> static __init int efivarfs_init(void)
> --
> 2.42.0.rc1.204.g551eb34607-goog
>
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