linux-kernel - Re: [PATCH 4/8] cifs: Fix creating NFS-style char/block devices

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Message-ID: <20240929004439.4xgymuv3mnr3n4a3@pali>
Date: Sun, 29 Sep 2024 02:44:39 +0200
From: Pali Rohár <pali@...nel.org>
To: Steve French <smfrench@...il.com>
Cc: Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>,
	linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] cifs: Fix creating NFS-style char/block devices

Ops, sorry for that. I just let my work branch on v6.11-rc7 and here
this change was not yet. But it is funny that we have hit this problem
independently in nearly same time.

On Saturday 28 September 2024 19:18:26 Steve French wrote:
> Looks like a duplicate of Paulo's earlier already merged patch, so
> will skip this one.  Reviewing the others in the series now.
> 
> commit a9de67336a4aa3ff2e706ba023fb5f7ff681a954
> Author: Paulo Alcantara <pc@...guebit.com>
> Date:   Wed Sep 18 21:53:35 2024 -0300
> 
>     smb: client: set correct device number on nfs reparse points
> 
>     Fix major and minor numbers set on special files created with NFS
>     reparse points.
> 
> On Sat, Sep 28, 2024 at 5:02 PM Pali Rohár <pali@...nel.org> wrote:
> >
> > Linux SMB client currently creates NFS-style char and block devices with
> > swapped major and minor numbers.
> >
> > Per MS-FSCC 2.1.2.6 NFS_SPECFILE_CHR and NFS_SPECFILE_BLK DataBuffer's
> > field contains two 32-bit integers that represent major and minor device
> > numbers.
> >
> > So the first one 32-bit integer in DataBuffer is major number and second
> > one in DataBuffer is minor number. Microsoft Windows NFS server reads them
> > in this order too.
> >
> > But Linux CIFS client creates new reparse point DataBuffer with minor
> > number first and major number second.
> >
> > Fix this problem in Linux SMB client and puts major and minor number in
> > the correct order into DataBuffer.
> >
> > This change fixes interoperability of char and block devices on Windows
> > share which is exported over both SMB and NFS protocols.
> >
> > Fixes: 102466f303ff ("smb: client: allow creating special files via reparse points")
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > ---
> >  fs/smb/client/reparse.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
> > index 48c27581ec51..63984796721a 100644
> > --- a/fs/smb/client/reparse.c
> > +++ b/fs/smb/client/reparse.c
> > @@ -108,8 +108,8 @@ static int nfs_set_reparse_buf(struct reparse_posix_data *buf,
> >         buf->InodeType = cpu_to_le64(type);
> >         buf->ReparseDataLength = cpu_to_le16(len + dlen -
> >                                              sizeof(struct reparse_data_buffer));
> > -       *(__le64 *)buf->DataBuffer = cpu_to_le64(((u64)MAJOR(dev) << 32) |
> > -                                                MINOR(dev));
> > +       *(__le64 *)buf->DataBuffer = cpu_to_le64(((u64)MINOR(dev) << 32) |
> > +                                                MAJOR(dev));
> >         iov->iov_base = buf;
> >         iov->iov_len = len + dlen;
> >         return 0;
> > --
> > 2.20.1
> >
> >
> 
> 
> -- 
> Thanks,
> 
> Steve