From 5329aa5101f73c451bcd48deaf3f296685849d9c Mon Sep 17 00:00:00 2001 From: Jiao Zhou Date: Fri, 20 Oct 2023 00:46:39 +0200 Subject: efivarfs: Add uid/gid mount options Allow UEFI variables to be modified by non-root processes in order to run sandboxed code. This doesn't change the behavior of mounting efivarfs unless uid/gid are specified; by default both are set to root. Signed-off-by: Jiao Zhou Acked-by: Matthew Garrett Signed-off-by: Ard Biesheuvel --- fs/efivarfs/inode.c | 4 +++ fs/efivarfs/internal.h | 9 +++++++ fs/efivarfs/super.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 81 insertions(+) (limited to 'fs/efivarfs') diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c index db9231f0e77b..92e5e060e0ee 100644 --- a/fs/efivarfs/inode.c +++ b/fs/efivarfs/inode.c @@ -21,8 +21,12 @@ struct inode *efivarfs_get_inode(struct super_block *sb, dev_t dev, bool is_removable) { struct inode *inode = new_inode(sb); + struct efivarfs_fs_info *fsi = sb->s_fs_info; + 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_set_ctime_current(inode); diff --git a/fs/efivarfs/internal.h b/fs/efivarfs/internal.h index 8ebf3a6a8aa2..c66647f5c0bd 100644 --- a/fs/efivarfs/internal.h +++ b/fs/efivarfs/internal.h @@ -9,6 +9,15 @@ #include #include +struct efivarfs_mount_opts { + kuid_t uid; + kgid_t gid; +}; + +struct efivarfs_fs_info { + struct efivarfs_mount_opts mount_opts; +}; + struct efi_variable { efi_char16_t VariableName[EFI_VAR_NAME_LEN/sizeof(efi_char16_t)]; efi_guid_t VendorGuid; diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index e028fafa04f3..46c6446ec280 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -24,6 +25,21 @@ 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; + + 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 int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf) { const u32 attr = EFI_VARIABLE_NON_VOLATILE | @@ -64,6 +80,7 @@ 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 +242,45 @@ 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); + if (!uid_valid(opts->uid)) + return -EINVAL; + break; + case Opt_gid: + opts->gid = make_kgid(current_user_ns(), result.uint_32); + if (!gid_valid(opts->gid)) + return -EINVAL; + break; + default: + return -EINVAL; + } + + return 0; +} + static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc) { struct inode *inode = NULL; @@ -271,10 +327,21 @@ 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(*sfi), GFP_KERNEL); + if (!sfi) + return -ENOMEM; + + sfi->mount_opts.uid = GLOBAL_ROOT_UID; + sfi->mount_opts.gid = GLOBAL_ROOT_GID; + + fc->s_fs_info = sfi; fc->ops = &efivarfs_context_ops; return 0; } @@ -295,6 +362,7 @@ 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) -- cgit