We want to support fwupd for updating system firmware on Reven. Capsule updates need to create UEFI variables. Our current approach to UEFI variables of just allowing access to a static list of them at boot time won't work here. I think we could add mount options to efivarfs to set the uid/gid. We'd then mount the file system with fwupd's uid/gid. This approach is used by a number of other filesystems that don't have native support for ownership, so it should be upstreamable. Signed-off-by: Jiao Zhou <jiaozhou@xxxxxxxxxx> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> Closes: https://lore.kernel.org/oe-lkp/202308291443.ea96ac66-oliver.sang@xxxxxxxxx --- Changelog since v2: - Fix a NULL pointer dereference and add a a trailing empty entry to sturct. fs/efivarfs/inode.c | 4 +++ fs/efivarfs/internal.h | 9 ++++++ fs/efivarfs/super.c | 65 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 78 insertions(+) diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c index 939e5e242b98..de57fb6c28e1 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 30ae44cb7453..57deaf56d8e2 100644 --- a/fs/efivarfs/internal.h +++ b/fs/efivarfs/internal.h @@ -8,6 +8,15 @@ #include <linux/list.h> +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 15880a68faad..d67b0d157ff5 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> @@ -23,10 +24,27 @@ static void efivarfs_evict_inode(struct inode *inode) clear_inode(inode); } +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 = simple_statfs, .drop_inode = generic_delete_inode, .evict_inode = efivarfs_evict_inode, + .show_options = efivarfs_show_options, }; /* @@ -190,6 +208,41 @@ 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; @@ -233,10 +286,21 @@ 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) { + struct efivarfs_fs_info *sfi; + + sfi = kzalloc(sizeof(struct efivarfs_fs_info), GFP_KERNEL); + if (!sfi) + return -ENOMEM; + + sfi->mount_opts.uid = current_uid(); + sfi->mount_opts.gid = current_gid(); + + fc->s_fs_info = sfi; fc->ops = &efivarfs_context_ops; return 0; } @@ -254,6 +318,7 @@ 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.rc2.253.gd59a3bf2b4-goog
