Re: [PATCH RFC 5/6] exportfs: add permission method

Jan Kara
2024-12-02T16:04:54Z

On Fri 29-11-24 14:38:04, Christian Brauner wrote:
> This allows filesystems such as pidfs to provide their custom permission
> checks.
>
> Signed-off-by: Christian Brauner <brauner@kernel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/fhandle.c | 21 +++++++--------------
> include/linux/exportfs.h | 17 ++++++++++++++++-
> 2 files changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/fs/fhandle.c b/fs/fhandle.c
> index 031ad5592a0beabcc299436f037ad5fe626332e6..23491094032ec037066a271873ea8ff794616bee 100644
> --- a/fs/fhandle.c
> +++ b/fs/fhandle.c
> @@ -187,17 +187,6 @@ static int get_path_from_fd(int fd, struct path *root)
> return 0;
> }
>
> -enum handle_to_path_flags {
> - HANDLE_CHECK_PERMS = (1 << 0),
> - HANDLE_CHECK_SUBTREE = (1 << 1),
> -};
> -
> -struct handle_to_path_ctx {
> - struct path root;
> - enum handle_to_path_flags flags;
> - unsigned int fh_flags;
> -};
> -
> static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
> {
> struct handle_to_path_ctx *ctx = context;
> @@ -335,15 +324,19 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
> struct file_handle f_handle;
> struct file_handle *handle = NULL;
> struct handle_to_path_ctx ctx = {};
> + const struct export_operations *eops;
>
> retval = get_path_from_fd(mountdirfd, &ctx.root);
> if (retval)
> goto out_err;
>
> - if (!may_decode_fh(&ctx, o_flags)) {
> - retval = -EPERM;
> + eops = ctx.root.mnt->mnt_sb->s_export_op;
> + if (eops && eops->permission)
> + retval = eops->permission(&ctx, o_flags);
> + else
> + retval = may_decode_fh(&ctx, o_flags);
> + if (retval)
> goto out_path;
> - }
>
> if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
> retval = -EFAULT;
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index c69b79b64466d5bc32ffe9b2796a388130fe72d8..a087606ace194ccc9d1250f990ce55627aaf8dc5 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -3,6 +3,7 @@
> #define LINUX_EXPORTFS_H 1
>
> #include <linux/types.h>
> +#include <linux/path.h>
>
> struct dentry;
> struct iattr;
> @@ -10,7 +11,6 @@ struct inode;
> struct iomap;
> struct super_block;
> struct vfsmount;
> -struct path;
>
> /* limit the handle size to NFSv4 handle size now */
> #define MAX_HANDLE_SZ 128
> @@ -157,6 +157,17 @@ struct fid {
> };
> };
>
> +enum handle_to_path_flags {
> + HANDLE_CHECK_PERMS = (1 << 0),
> + HANDLE_CHECK_SUBTREE = (1 << 1),
> +};
> +
> +struct handle_to_path_ctx {
> + struct path root;
> + enum handle_to_path_flags flags;
> + unsigned int fh_flags;
> +};
> +
> #define EXPORT_FH_CONNECTABLE 0x1 /* Encode file handle with parent */
> #define EXPORT_FH_FID 0x2 /* File handle may be non-decodeable */
> #define EXPORT_FH_DIR_ONLY 0x4 /* Only decode file handle for a directory */
> @@ -226,6 +237,9 @@ struct fid {
> * is also a directory. In the event that it cannot be found, or storage
> * space cannot be allocated, a %ERR_PTR should be returned.
> *
> + * permission:
> + * Allow filesystems to specify a custom permission function.
> + *
> * open:
> * Allow filesystems to specify a custom open function.
> *
> @@ -255,6 +269,7 @@ struct export_operations {
> bool write, u32 *device_generation);
> int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
> int nr_iomaps, struct iattr *iattr);
> + int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
> struct file * (*open)(struct path *path, unsigned int oflags);
> #define EXPORT_OP_NOWCC (0x1) /* don't collect v3 wcc data */
> #define EXPORT_OP_NOSUBTREECHK (0x2) /* no subtree checking */
>
> --
> 2.45.2
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR