Re: [PATCH 03/10] mount_service: refuse OPEN after the MNTPT request

[Bernd Schubert <bernd@bsbernd.com>]

On 9/26/26 00:07, Darrick J. Wong wrote:
> On Fri, Sep 25, 2026 at 12:23:31AM +0200, Bernd Schubert via B4 Relay wrote:
>> From: Bernd Schubert <bernd@bsbernd.com>
>>
>> The fuse server sends fuservicemount3 a series of requests: OPEN for
>> its backing file, MNTPT to name the mount point, then MOUNT. The server
>> chooses the order. For a directory mount point, attach_to_mountpoint()
>> changes the working directory of the helper to the mount point. The
>> helper then mounts on ".", so a rename of the path cannot redirect the
>> mount.
>>
>> A relative path in an OPEN request after MNTPT resolved inside the
>> mount point. For "fuservicemount3 disk.img /mnt -t fuse.service_ll",
>> an OPEN of "disk.img" matched the command line argument, but the helper
>> opened /mnt/disk.img, not disk.img in the user's working directory. The
>> helper now refuses OPEN once the mount point is set. No in-tree server
>> sends OPEN after MNTPT.
> 
> How about absolute paths?  The resolution of those remain the same after
> the cwd changes.

Next version switches to openat and should handle all of that.


Thanks,
Bernd