Re: [PATCH] ceph: use the mount idmap for the owner checks in the SET_LAYOUT ioctls

[Xiubo Li]

Hi Ilya,

I'm not sure why I couldn't find the original email of this. I checked
the changes on lore.kernel.org.

The fix looks correct to me.

On an idmapped mount, using &nop_mnt_idmap compares the caller's fsuid
against the unmapped on-disk uid directly, which would wrongly deny
the actual mapped owner and potentially allow an unrelated caller.
Both functions already have the struct file, so switching to
file_mnt_idmap(file) is the right thing to do.

Reviewed-by: Xiubo Li <xiubo.li@xxxxxxxxx>

Thanks
Xiubo Li

On Sun, 9 Aug 2026 at 10:33, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>
> On Sat, Aug 8, 2026 at 8:31 AM Max Kellermann <max.kellermann@xxxxxxxxx> wrote:
> >
> > On Tue, Jul 28, 2026 at 1:31 PM Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
> > > Was there any specific reason you used nop_mnt_idmap for these checks?
> >
> > No, I copied that check from another filesystem, probably ext2. I had
> > no idea what this parameter means (and I have never used idmappings).
> > I guess the amended parameter in this patch is correct.
>
> Hi Xiubo,
>
> You reviewed Max's "ceph: add owner/capability checks for
> CEPH_IOC_SET_LAYOUT*" patch.  Would you be able to review this fixup as
> well?
>
> Thanks,
>
>                 Ilya