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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
3 changed files with 33 additions and 2 deletions
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7
fs/fhandle.c
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@@ -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: