On Fri, Jan 20, 2023 at 10:43:46AM +0100, Giuseppe Scrivano wrote:
> This patch enables idmapped mounts for tmpfs when CONFIG_SHMEM is defined.
> Since all dedicated helpers for this functionality exist, in this
> patch we just pass down the idmap argument from the VFS methods to the
> relevant helpers.
>
> Signed-off-by: Giuseppe Scrivano <gscrivan@xxxxxxxxxx>
> Tested-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
LGTM.
Reviewed-by: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx>
> ---
> mm/shmem.c | 47 ++++++++++++++++++++++++++++-------------------
> 1 file changed, 28 insertions(+), 19 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 028675cd97d4..2fdd76ab337f 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1068,7 +1068,7 @@ static int shmem_getattr(struct mnt_idmap *idmap,
> stat->attributes_mask |= (STATX_ATTR_APPEND |
> STATX_ATTR_IMMUTABLE |
> STATX_ATTR_NODUMP);
> - generic_fillattr(&nop_mnt_idmap, inode, stat);
> + generic_fillattr(idmap, inode, stat);
>
> if (shmem_is_huge(NULL, inode, 0, false))
> stat->blksize = HPAGE_PMD_SIZE;
> @@ -1091,7 +1091,7 @@ static int shmem_setattr(struct mnt_idmap *idmap,
> bool update_mtime = false;
> bool update_ctime = true;
>
> - error = setattr_prepare(&nop_mnt_idmap, dentry, attr);
> + error = setattr_prepare(idmap, dentry, attr);
> if (error)
> return error;
>
> @@ -1129,9 +1129,9 @@ static int shmem_setattr(struct mnt_idmap *idmap,
> }
> }
>
> - setattr_copy(&nop_mnt_idmap, inode, attr);
> + setattr_copy(idmap, inode, attr);
> if (attr->ia_valid & ATTR_MODE)
> - error = posix_acl_chmod(&nop_mnt_idmap, dentry, inode->i_mode);
> + error = posix_acl_chmod(idmap, dentry, inode->i_mode);
> if (!error && update_ctime) {
> inode->i_ctime = current_time(inode);
> if (update_mtime)
> @@ -2329,8 +2329,9 @@ static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
> #define shmem_initxattrs NULL
> #endif
>
> -static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
> - umode_t mode, dev_t dev, unsigned long flags)
> +static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block *sb,
> + struct inode *dir, umode_t mode, dev_t dev,
> + unsigned long flags)
> {
> struct inode *inode;
> struct shmem_inode_info *info;
> @@ -2343,7 +2344,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
> inode = new_inode(sb);
> if (inode) {
> inode->i_ino = ino;
> - inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
> + inode_init_owner(idmap, inode, dir, mode);
> inode->i_blocks = 0;
> inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
> inode->i_generation = get_random_u32();
> @@ -2921,7 +2922,7 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
> struct inode *inode;
> int error = -ENOSPC;
>
> - inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
> + inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, dev, VM_NORESERVE);
> if (inode) {
> error = simple_acl_create(dir, inode);
> if (error)
> @@ -2952,7 +2953,7 @@ shmem_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
> struct inode *inode;
> int error = -ENOSPC;
>
> - inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
> + inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, 0, VM_NORESERVE);
> if (inode) {
> error = security_inode_init_security(inode, dir,
> NULL,
> @@ -2975,8 +2976,8 @@ static int shmem_mkdir(struct mnt_idmap *idmap, struct inode *dir,
> {
> int error;
>
> - if ((error = shmem_mknod(&nop_mnt_idmap, dir, dentry,
> - mode | S_IFDIR, 0)))
> + error = shmem_mknod(idmap, dir, dentry, mode | S_IFDIR, 0);
> + if (error)
> return error;
> inc_nlink(dir);
> return 0;
> @@ -2985,7 +2986,7 @@ static int shmem_mkdir(struct mnt_idmap *idmap, struct inode *dir,
> static int shmem_create(struct mnt_idmap *idmap, struct inode *dir,
> struct dentry *dentry, umode_t mode, bool excl)
> {
> - return shmem_mknod(&nop_mnt_idmap, dir, dentry, mode | S_IFREG, 0);
> + return shmem_mknod(idmap, dir, dentry, mode | S_IFREG, 0);
> }
>
> /*
> @@ -3055,7 +3056,7 @@ static int shmem_whiteout(struct mnt_idmap *idmap,
> if (!whiteout)
> return -ENOMEM;
>
> - error = shmem_mknod(&nop_mnt_idmap, old_dir, whiteout,
> + error = shmem_mknod(idmap, old_dir, whiteout,
> S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
> dput(whiteout);
> if (error)
> @@ -3098,7 +3099,7 @@ static int shmem_rename2(struct mnt_idmap *idmap,
> if (flags & RENAME_WHITEOUT) {
> int error;
>
> - error = shmem_whiteout(&nop_mnt_idmap, old_dir, old_dentry);
> + error = shmem_whiteout(idmap, old_dir, old_dentry);
> if (error)
> return error;
> }
> @@ -3136,7 +3137,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
> if (len > PAGE_SIZE)
> return -ENAMETOOLONG;
>
> - inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
> + inode = shmem_get_inode(idmap, dir->i_sb, dir, S_IFLNK | 0777, 0,
> VM_NORESERVE);
> if (!inode)
> return -ENOSPC;
> @@ -3819,7 +3820,8 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
> #endif
> uuid_gen(&sb->s_uuid);
>
> - inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
> + inode = shmem_get_inode(&nop_mnt_idmap, sb, NULL, S_IFDIR | sbinfo->mode, 0,
> + VM_NORESERVE);
> if (!inode)
> goto failed;
> inode->i_uid = sbinfo->uid;
> @@ -4044,7 +4046,11 @@ static struct file_system_type shmem_fs_type = {
> .parameters = shmem_fs_parameters,
> #endif
> .kill_sb = kill_litter_super,
> +#ifdef CONFIG_SHMEM
> + .fs_flags = FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
> +#else
> .fs_flags = FS_USERNS_MOUNT,
> +#endif
> };
>
> void __init shmem_init(void)
> @@ -4196,7 +4202,7 @@ EXPORT_SYMBOL_GPL(shmem_truncate_range);
> #define shmem_vm_ops generic_file_vm_ops
> #define shmem_anon_vm_ops generic_file_vm_ops
> #define shmem_file_operations ramfs_file_operations
> -#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
> +#define shmem_get_inode(idmap, sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
> #define shmem_acct_size(flags, size) 0
> #define shmem_unacct_size(flags, size) do {} while (0)
>
> @@ -4219,8 +4225,11 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l
> if (shmem_acct_size(flags, size))
> return ERR_PTR(-ENOMEM);
>
> - inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
> - flags);
> + if (is_idmapped_mnt(mnt))
> + return ERR_PTR(-EINVAL);
> +
> + inode = shmem_get_inode(&nop_mnt_idmap, mnt->mnt_sb, NULL,
> + S_IFREG | S_IRWXUGO, 0, flags);
> if (unlikely(!inode)) {
> shmem_unacct_size(flags, size);
> return ERR_PTR(-ENOSPC);
> --
> 2.38.1
>
--
Seth
