[PATCH] Cygwin: Fix access to block devices below /proc/sys.

[Corinna Vinschen]

On Nov 30 13:49, Christian Franke wrote:
> Corinna Vinschen wrote:
> > On Nov 28 22:59, Christian Franke wrote:
> > > ...
> > > The attached experimental patch does not fix the lseek() (sorry), but
> > > handles such block devices with fhandler_dev_floppy instead. Tested with
> > > above use cases.
> > > 
> > > I'm not sure whether this could break access to other /proc/sys block
> > > devices. This would happen if fh->exists() returns virt_blk for devices
> > > which do not support IOCTL_DISK_GET_DRIVE_GEOMETRY* or
> > > IOCTL_DISK_GET_PARTITION_INFO*.
> > Pushed, becasue it's a nice idea.  The above problem shouldn't happen,
> > in theory, but I'm not sure.  virt_blk is generated for devices types
> > 
> >    FILE_DEVICE_DISK
> >    FILE_DEVICE_CD_ROM
> >    FILE_DEVICE_VIRTUAL_DISK
> >    FILE_DEVICE_DFS
> >    FILE_DEVICE_NETWORK_FILE_SYSTEM
> > 
> > FILE_DEVICE_DFS or FILE_DEVICE_NETWORK_FILE_SYSTEM might be a problem,
> > but there should be a way to workaround that, if necessary, isn't it?
> > Maybe it's a bad idea to treat those as blk devices at all?
> 
> Could anything be read from such a node? If yes, treat as character device?
> 
> If no and /proc/sys/foo/bar/some/path allows access to /some/path behind
> DFS/NFS node /proc/sys/foo/bar, then treat as directory?
> 
> This is already the case for SMB shares:
> 
> $ ls -ld /proc/sys/DosDevices/X:
> lr-------- 1 ... 0 Nov 30 13:10 /proc/sys/DosDevices/X: ->
>   /proc/sys/Device/LanmanRedirector/;X:..../127.0.0.1/Share
> 
> $ ls -lLd /proc/sys/DosDevices/X:
> drwxr-xr-x 1 ... 0 Nov 14 09:06 /proc/sys/DosDevices/X:
> 
> $ ls -L /proc/sys/DosDevices/X:
> ... files on this share

...and it's already the case for NFS shares, too:

$ ls -ld /proc/sys/DosDevices/Y:
lr-------- 1 corinna vinschen 0 Nov 30 14:59 /proc/sys/DosDevices/Y: -> /proc/sys/Device/MRxNfs/;Y:00000000001cb27f/...

$ ls -lLd /proc/sys/DosDevices/Y:
drwxr-xr-x 5 corinna vinschen 41 May 19  2016 /proc/sys/DosDevices/Y:

That means we don't have to handle FILE_DEVICE_NETWORK_FILE_SYSTEM in
the code creating the virt_blk device type at all.  I have high hopes
this is the same for DFS, albeit I can't test it...


Thanks,
Corinna