Unverified Commit 4a530a7c authored by Amir Goldstein's avatar Amir Goldstein Committed by Christian Brauner
Browse files

fs: prepare for "explicit connectable" file handles 



We would like to use the high 16bit of the handle_type field to encode
file handle traits, such as "connectable".

In preparation for this change, make sure that filesystems do not return
a handle_type value with upper bits set and that the open_by_handle_at(2)
syscall rejects these handle types.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20241011090023.655623-2-amir73il@gmail.com


Fixes: 570df4e9 ("ceph: snapshot nfs re-export")
Acked-by:
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 8e929cb5

fs/exportfs/expfs.c

+15 −2
Original line number Diff line number Diff line
@@ -382,14 +382,24 @@ int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid, 
			     int *max_len, struct inode *parent, int flags)

{

	const struct export_operations *nop = inode->i_sb->s_export_op;

	enum fid_type type;



	if (!exportfs_can_encode_fh(nop, flags))

		return -EOPNOTSUPP;



	if (!nop && (flags & EXPORT_FH_FID))

		return exportfs_encode_ino64_fid(inode, fid, max_len);

		type = exportfs_encode_ino64_fid(inode, fid, max_len);

	else

		type = nop->encode_fh(inode, fid->raw, max_len, parent);



	if (type > 0 && FILEID_USER_FLAGS(type)) {

		pr_warn_once("%s: unexpected fh type value 0x%x from fstype %s.\n",

			     __func__, type, inode->i_sb->s_type->name);

		return -EINVAL;

	}



	return type;



	return nop->encode_fh(inode, fid->raw, max_len, parent);

}

EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
@@ -436,6 +446,9 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len, 
	char nbuf[NAME_MAX+1];

	int err;



	if (fileid_type < 0 || FILEID_USER_FLAGS(fileid_type))

		return ERR_PTR(-EINVAL);



	/*

	 * Try to get any dentry for the given file handle from the filesystem.

	 */

fs/fhandle.c

+7 −0
Original line number Diff line number Diff line
@@ -307,6 +307,11 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 
		retval = -EINVAL;

		goto out_path;

	}

	if (f_handle.handle_type < 0 ||

	    FILEID_USER_FLAGS(f_handle.handle_type) & ~FILEID_VALID_USER_FLAGS) {

		retval = -EINVAL;

		goto out_path;

	}

	handle = kmalloc(struct_size(handle, f_handle, f_handle.handle_bytes),

			 GFP_KERNEL);

	if (!handle) {
@@ -322,6 +327,8 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 
		goto out_handle;

	}



	/* Filesystem code should not be exposed to user flags */

	handle->handle_type &= ~FILEID_USER_FLAGS_MASK;

	retval = do_handle_to_path(handle, path, &ctx);



out_handle:

include/linux/exportfs.h

+11 −0
Original line number Diff line number Diff line
@@ -160,6 +160,17 @@ struct fid { 
#define EXPORT_FH_FID		0x2 /* File handle may be non-decodeable */

#define EXPORT_FH_DIR_ONLY	0x4 /* Only decode file handle for a directory */



/*

 * Filesystems use only lower 8 bits of file_handle type for fid_type.

 * name_to_handle_at() uses upper 16 bits of type as user flags to be

 * interpreted by open_by_handle_at().

 */

#define FILEID_USER_FLAGS_MASK	0xffff0000

#define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK)



/* Flags supported in encoded handle_type that is exported to user */

#define FILEID_VALID_USER_FLAGS	(0)



/**

 * struct export_operations - for nfsd to communicate with file systems

 * @encode_fh:      encode a file handle fragment from a dentry