Re: [PATCH 2/2] fs: return EOPNOTSUPP from file_setattr/file_getattr syscalls

[Andrey Albershteyn]

On 2025-10-09 10:20:41, Darrick J. Wong wrote:
> On Wed, Oct 08, 2025 at 02:44:18PM +0200, Andrey Albershteyn wrote:
> > These syscalls call to vfs_fileattr_get/set functions which return
> > ENOIOCTLCMD if filesystem doesn't support setting file attribute on an
> > inode. For syscalls EOPNOTSUPP would be more appropriate return error.
> > 
> > Signed-off-by: Andrey Albershteyn <aalbersh@xxxxxxxxxx>
> > ---
> >  fs/file_attr.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/fs/file_attr.c b/fs/file_attr.c
> > index 460b2dd21a85..5e3e2aba97b5 100644
> > --- a/fs/file_attr.c
> > +++ b/fs/file_attr.c
> > @@ -416,6 +416,8 @@ SYSCALL_DEFINE5(file_getattr, int, dfd, const char __user *, filename,
> >  	}
> >  
> >  	error = vfs_fileattr_get(filepath.dentry, &fa);
> > +	if (error == -ENOIOCTLCMD)
> 
> Hrm.  Back in 6.17, XFS would return ENOTTY if you called ->fileattr_get
> on a special file:
> 
> int
> xfs_fileattr_get(
> 	struct dentry		*dentry,
> 	struct file_kattr	*fa)
> {
> 	struct xfs_inode	*ip = XFS_I(d_inode(dentry));
> 
> 	if (d_is_special(dentry))
> 		return -ENOTTY;
> 	...
> }
> 
> Given that there are other fileattr_[gs]et implementations out there
> that might return ENOTTY (e.g. fuse servers and other externally
> maintained filesystems), I think both syscall functions need to check
> for that as well:
> 
> 	if (error == -ENOIOCTLCMD || error == -ENOTTY)
> 		return -EOPNOTSUPP;

Make sense (looks like ubifs, jfs and gfs2 also return ENOTTY for
special files), I haven't found ENOTTY being used for anything else
there

-- 
- Andrey