Re: [PATCH RESEND 06/11] cifs: Validate presence of EA $LXMOD for WSL reparse points

["Pali Rohár" <pali@kernel.org>]

With this change applied, such nodes are recognized as "regular files" same as in WSL.

On Monday 06 July 2026 17:30:35 Steve French wrote:
> If this EA is missing, does Linux client still recognize it (not
> talking about WSL just what Linux client would see)?
> 
> On Mon, Jul 6, 2026 at 1:51 PM Pali Rohár <pali@kernel.org> wrote:
> >
> > S_DT part of xattr $LXMOD is mandatory for all WSL reparse points except the
> > WSL symlink and Win32 socket. Microsoft WSL subsystem does not recognize
> > them without xattr $LXMOD too, and treat such inodes as regular files.
> >
> > Fixes: ef201e8759d2 ("cifs: Validate EAs for WSL reparse points")
> > Fixes: 78e26bec4d6d ("smb: client: parse uid, gid, mode and dev from WSL reparse points")
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > ---
> >  fs/smb/client/reparse.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
> > index 49a6a0cc2b61..99e93b56374f 100644
> > --- a/fs/smb/client/reparse.c
> > +++ b/fs/smb/client/reparse.c
> > @@ -1124,6 +1124,7 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
> >  {
> >         struct smb2_file_full_ea_info *ea;
> >         bool ignore_missing_eas = false;
> > +       bool have_xattr_mode = false;
> >         bool have_xattr_dev = false;
> >         umode_t reparse_mode_type = 0;
> >         u32 next = 0;
> > @@ -1183,6 +1184,7 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
> >                         if (S_DT(reparse_mode_type) != S_DT(le32_to_cpu(*(__le32 *)v)))
> >                                 return false;
> >                         fattr->cf_mode = (umode_t)le32_to_cpu(*(__le32 *)v);
> > +                       have_xattr_mode = true;
> >                 } else if (!strncmp(name, SMB2_WSL_XATTR_DEV, nlen)) {
> >                         fattr->cf_rdev = reparse_mkdev(v);
> >                         have_xattr_dev = true;
> > @@ -1194,6 +1196,16 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
> >         if (!have_xattr_dev && (tag == IO_REPARSE_TAG_LX_CHR || tag == IO_REPARSE_TAG_LX_BLK))
> >                 return ignore_missing_eas;
> >
> > +       /*
> > +        * S_DT part of xattr MODE is mandatory for all WSL reparse points except the WSL symlink.
> > +        * Microsoft WSL does not recognize them without xattr MODE too (except the WSL symlink).
> > +        * IO_REPARSE_TAG_AF_UNIX is here an exception because this reparse point is used by both
> > +        * WSL subsystem and native NT/WinAPI subsystems. And NT/WinAPI creates AF UNIX socket
> > +        * without the xattr MODE and recognize it also without the xattr MODE.
> > +        */
> > +       if (!have_xattr_mode && (tag != IO_REPARSE_TAG_AF_UNIX && tag != IO_REPARSE_TAG_LX_SYMLINK))
> > +               return ignore_missing_eas;
> > +
> >         fattr->cf_mode |= reparse_mode_type;
> >         return true;
> >  }
> > --
> > 2.20.1
> >
> >
> 
> 
> -- 
> Thanks,
> 
> Steve