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fs: prepare for "explicit connectable" file handles

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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: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20241011090023.655623-2-amir73il@gmail.com
Fixes: 570df4e9c2 ("ceph: snapshot nfs re-export")
Acked-by:
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Amir Goldstein 2024-10-11 11:00:21 +02:00 committed by Christian Brauner
parent 8e929cb546
commit 4a530a7c75
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
3 changed files with 33 additions and 2 deletions
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17
fs/exportfs/expfs.c
View File

@ -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.
*/

7
fs/fhandle.c
View File

@ -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:

11
include/linux/exportfs.h
View File

@ -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