Re: [PATCH v2 1/4] md/raid10: fix null-ptr-deref of mreplace in raid10_sync_request

[Li Nan]

在 2023/5/27 5:38, Song Liu 写道:
> On Fri, May 26, 2023 at 12:47 AM <linan666@xxxxxxxxxxxxxxx> wrote:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > need_replace will be set to 1 if no-Faulty mreplace exists, and mreplace
> > will be deref later. However, the latter check of mreplace might set
> > mreplace to NULL, null-ptr-deref occurs if need_replace is 1 at this time.
> >
> > Fix it by merging two checks into one. And replace 'need_replace' with
> > 'mreplace' because their values are always the same.
> >
> > Fixes: ee37d7314a32 ("md/raid10: Fix raid10 replace hang when new added disk faulty")
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >   drivers/md/raid10.c | 13 +++++--------
> >   1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> > index 4fcfcb350d2b..e21502c03b45 100644
> > --- a/drivers/md/raid10.c
> > +++ b/drivers/md/raid10.c
> > @@ -3438,7 +3438,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
> >                          int must_sync;
> >                          int any_working;
> >                          int need_recover = 0;
> > -                       int need_replace = 0;
> >                          struct raid10_info *mirror = &conf->mirrors[i];
> >                          struct md_rdev *mrdev, *mreplace;
> >
> > @@ -3451,10 +3450,10 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
> >                              !test_bit(In_sync, &mrdev->flags))
> >                                  need_recover = 1;
> >                          if (mreplace != NULL &&
> > -                           !test_bit(Faulty, &mreplace->flags))
> > -                               need_replace = 1;
> > +                           test_bit(Faulty, &mreplace->flags))
> > +                               mreplace = NULL;
> >
> > -                       if (!need_recover && !need_replace) {
> > +                       if (!need_recover && !mreplace) {
> >                                  rcu_read_unlock();
> >                                  continue;
> >                          }
> > @@ -3470,8 +3469,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
> >                                  rcu_read_unlock();
> >                                  continue;
> >                          }
>
> To make sure I understand the issue correctly:
>
> The null-ptr-deref only happens when the Faulty bit was set after the
> last check and before this check below, right?

Yes. I will improve log in next version.

--
Thanks,
Nan