On Thu, Aug 31, 2023 at 03:31:07PM +0000, Jiao Zhou 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. > > TEST=FEATURES=test emerge-reven chromeos-kernel-5_15 > > 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 > --- > 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; This will allow the following: # initial user namespace fd_fs = fsopen("efivarfs") # switch to some unprivileged userns fsconfig(fd_fs, FSCONFIG_SET_STRING, "uid", "1000") ==> This now resolves within the caller's user namespace which might have an idmapping where 1000 cannot be resolved causing sb->{g,u}id to be set to INVALID_{G,U}ID. In fact this is also possible in your patch right now without the namespace switching. The caller could just pass -1 and that would cause inodes with INVALID_{G,U}ID to be created. So you want a check for {g,u}id_valid(). # send fd back to init_user_ns fsconfig(fd_fs, FSCONFIG_CMD_CREATE) fd_mnt = fsmount(fd_fs, ...) move_mount(fd_fs, "", -EBADF, "/somehwere", ...)
