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Merge tag 'vfs-6.13.exportfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

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Pull vfs exportfs updates from Christian Brauner:
 "This contains work to bring NFS connectable file handles to userspace
  servers.

  The name_to_handle_at() system call is extended to encode connectable
  file handles. Such file handles can be resolved to an open file with a
  connected path. So far userspace NFS servers couldn't make use of this
  functionality even though the kernel does already support it. This is
  achieved by introducing a new flag for name_to_handle_at().

  Similarly, the open_by_handle_at() system call is tought to understand
  connectable file handles explicitly created via name_to_handle_at()"

* tag 'vfs-6.13.exportfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  fs: open_by_handle_at() support for decoding "explicit connectable" file handles
  fs: name_to_handle_at() support for "explicit connectable" file handles
  fs: prepare for "explicit connectable" file handles
This commit is contained in:
Linus Torvalds
2024-11-26 13:26:15 -08:00
parent 9ad8d22f2f a312c10c01
commit 1675db5c42
4 changed files with 98 additions and 8 deletions
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75
fs/fhandle.c
View File

@@ -31,6 +31,14 @@ static long do_sys_name_to_handle(const struct path *path,
if (!exportfs_can_encode_fh(path->dentry->d_sb->s_export_op, fh_flags))
return -EOPNOTSUPP;
/*
* A request to encode a connectable handle for a disconnected dentry
* is unexpected since AT_EMPTY_PATH is not allowed.
*/
if (fh_flags & EXPORT_FH_CONNECTABLE &&
WARN_ON(path->dentry->d_flags & DCACHE_DISCONNECTED))
return -EINVAL;
if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
return -EFAULT;
@@ -45,7 +53,7 @@ static long do_sys_name_to_handle(const struct path *path,
/* convert handle size to multiple of sizeof(u32) */
handle_dwords = f_handle.handle_bytes >> 2;
/* we ask for a non connectable maybe decodeable file handle */
/* Encode a possibly decodeable/connectable file handle */
retval = exportfs_encode_fh(path->dentry,
(struct fid *)handle->f_handle,
&handle_dwords, fh_flags);
@@ -67,8 +75,23 @@ static long do_sys_name_to_handle(const struct path *path,
* non variable part of the file_handle
*/
handle_bytes = 0;
} else
} else {
/*
* When asked to encode a connectable file handle, encode this
* property in the file handle itself, so that we later know
* how to decode it.
* For sanity, also encode in the file handle if the encoded
* object is a directory and verify this during decode, because
* decoding directory file handles is quite different than
* decoding connectable non-directory file handles.
*/
if (fh_flags & EXPORT_FH_CONNECTABLE) {
handle->handle_type |= FILEID_IS_CONNECTABLE;
if (d_is_dir(path->dentry))
fh_flags |= FILEID_IS_DIR;
}
retval = 0;
}
/* copy the mount id */
if (unique_mntid) {
if (put_user(real_mount(path->mnt)->mnt_id_unique,
@@ -109,15 +132,30 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
{
struct path path;
int lookup_flags;
int fh_flags;
int fh_flags = 0;
int err;
if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID |
AT_HANDLE_MNT_ID_UNIQUE))
AT_HANDLE_MNT_ID_UNIQUE | AT_HANDLE_CONNECTABLE))
return -EINVAL;
/*
* AT_HANDLE_FID means there is no intention to decode file handle
* AT_HANDLE_CONNECTABLE means there is an intention to decode a
* connected fd (with known path), so these flags are conflicting.
* AT_EMPTY_PATH could be used along with a dfd that refers to a
* disconnected non-directory, which cannot be used to encode a
* connectable file handle, because its parent is unknown.
*/
if (flag & AT_HANDLE_CONNECTABLE &&
flag & (AT_HANDLE_FID | AT_EMPTY_PATH))
return -EINVAL;
else if (flag & AT_HANDLE_FID)
fh_flags |= EXPORT_FH_FID;
else if (flag & AT_HANDLE_CONNECTABLE)
fh_flags |= EXPORT_FH_CONNECTABLE;
lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0;
if (flag & AT_EMPTY_PATH)
lookup_flags |= LOOKUP_EMPTY;
err = user_path_at(dfd, name, lookup_flags, &path);
@@ -207,7 +245,13 @@ static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
if (!(ctx->flags & HANDLE_CHECK_SUBTREE) || d == root)
retval = 1;
WARN_ON_ONCE(d != root && d != root->d_sb->s_root);
/*
* exportfs_decode_fh_raw() does not call acceptable() callback with
* a disconnected directory dentry, so we should have reached either
* mount fd directory or sb root.
*/
if (ctx->fh_flags & EXPORT_FH_DIR_ONLY)
WARN_ON_ONCE(d != root && d != root->d_sb->s_root);
dput(d);
return retval;
}
@@ -306,6 +350,12 @@ 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) {
@@ -321,6 +371,19 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
goto out_handle;
}
/*
* If handle was encoded with AT_HANDLE_CONNECTABLE, verify that we
* are decoding an fd with connected path, which is accessible from
* the mount fd path.
*/
if (f_handle.handle_type & FILEID_IS_CONNECTABLE) {
ctx.fh_flags |= EXPORT_FH_CONNECTABLE;
ctx.flags |= HANDLE_CHECK_SUBTREE;
}
if (f_handle.handle_type & FILEID_IS_DIR)
ctx.fh_flags |= EXPORT_FH_DIR_ONLY;
/* 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: