Re: [PATCH] ceph: quota: Fix invalid pointer access in

[Xiubo Li]

On 11/15/23 21:25, Ilya Dryomov wrote:
> On Wed, Nov 15, 2023 at 2:17 PM Xiubo Li <xiubli@xxxxxxxxxx> wrote:
> > On 11/15/23 20:32, Ilya Dryomov wrote:
> > > On Wed, Nov 15, 2023 at 1:35 AM Xiubo Li <xiubli@xxxxxxxxxx> wrote:
> > > > On 11/14/23 23:31, Wenchao Hao wrote:
> > > > > This issue is reported by smatch, get_quota_realm() might return
> > > > > ERR_PTR, so we should using IS_ERR_OR_NULL here to check the return
> > > > > value.
> > > > >
> > > > > Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
> > > > > ---
> > > > >     fs/ceph/quota.c | 2 +-
> > > > >     1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
> > > > > index 9d36c3532de1..c4b2929c6a83 100644
> > > > > --- a/fs/ceph/quota.c
> > > > > +++ b/fs/ceph/quota.c
> > > > > @@ -495,7 +495,7 @@ bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
> > > > >         realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root),
> > > > >                                 QUOTA_GET_MAX_BYTES, true);
> > > > >         up_read(&mdsc->snap_rwsem);
> > > > > -     if (!realm)
> > > > > +     if (IS_ERR_OR_NULL(realm))
> > > > >                 return false;
> > > > >
> > > > >         spin_lock(&realm->inodes_with_caps_lock);
> > > > Good catch.
> > > >
> > > > Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx>
> > > >
> > > > We should CC the stable mail list.
> > > Hi Xiubo,
> > >
> > > What exactly is being fixed here?  get_quota_realm() is called with
> > > retry=true, which means that no errors can be returned -- EAGAIN, the
> > > only error that get_quota_realm() can otherwise generate, would be
> > > handled internally by retrying.
> > Yeah, that's true.
> >
> > > Am I missing something that makes this qualify for stable?
> > Actually it's just for the smatch check for now.
> >
> > IMO we shouldn't depend on the 'retry', just potentially for new changes
> > in future could return a ERR_PTR and cause potential bugs.
> At present, ceph_quota_is_same_realm() also depends on it -- note how
> old_realm isn't checked for errors at all and new_realm is only checked
> for EAGAIN there.
>
> > If that's not worth to make it for stable, let's remove it.
> Yes, let's remove it.  Please update the commit message as well, so
> that it's clear that this is squashing a static checker warning and
> doesn't actually fix any immediate bug.

WenChao,

Could update the commit comment and send the V2 ?

Thanks

- Xiubo


> Thanks,
>
>                  Ilya