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Thu, 16 Nov 2023 22:14:34 -0800 (PST) Message-ID: <31d14ae5-8d79-6e79-2e29-203d4062de7e@redhat.com> Date: Fri, 17 Nov 2023 14:14:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH] ceph: quota: Fix invalid pointer access in Content-Language: en-US To: Wenchao Hao , Ilya Dryomov Cc: Jeff Layton , ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, louhongxiang@huawei.com References: <20231114153108.1932884-1-haowenchao2@huawei.com> <5a1766c6-d923-a4e5-c5be-15b953372ef5@redhat.com> <5eb54f3e-3438-ba47-3d43-baf6b27aad0e@huawei.com> <6824ece2-33ee-63f4-2c7a-7033556325cb@redhat.com> <3a0b72e0-0784-0882-c18b-6178ed597670@huawei.com> From: Xiubo Li In-Reply-To: <3a0b72e0-0784-0882-c18b-6178ed597670@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/16/23 15:09, Wenchao Hao wrote: > On 2023/11/16 11:06, Xiubo Li wrote: >> >> On 11/16/23 10:54, Wenchao Hao wrote: >>> On 2023/11/15 21:34, Xiubo Li wrote: >>>> >>>> On 11/15/23 21:25, Ilya Dryomov wrote: >>>>> On Wed, Nov 15, 2023 at 2:17 PM Xiubo Li wrote: >>>>>> >>>>>> On 11/15/23 20:32, Ilya Dryomov wrote: >>>>>>> On Wed, Nov 15, 2023 at 1:35 AM Xiubo Li 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 >>>>>>>>> --- >>>>>>>>>     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 >>>>>>>> >>>>>>>> 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 ? >>>> >>> >>> OK, I would update the commit comment as following: >>> >>> This issue is reported by smatch, get_quota_realm() might return >>> ERR_PTR. It's not a immediate bug because get_quota_realm() is called >>> with 'retry=true', no errors can be returned. >>> >>> While we still should check the return value of get_quota_realm() with >>> IS_ERR_OR_NULL to avoid potential bugs if get_quota_realm() is changed >>> to return other ERR_PTR in future. >>> >>> What's more, should I change the ceph_quota_is_same_realm() too? >>> >> Yeah, please. Let's fix them all. >> > > is_same is return as true if both old_realm and new_realm are NULL, I > do not > want to change the origin logic except add check for ERR_PTR, so > following > is my change: > > 1. make sure xxx_realm is valid before calling ceph_put_snap_realm. > 2. return false if new_realm or old_realm is ERR_PTR, this is newly added >    and now we would always run with the else branch. > > diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c > index c4b2929c6a83..8da9ffb05395 100644 > --- a/fs/ceph/quota.c > +++ b/fs/ceph/quota.c > @@ -290,16 +290,20 @@ bool ceph_quota_is_same_realm(struct inode *old, > struct inode *new) >         new_realm = get_quota_realm(mdsc, new, QUOTA_GET_ANY, false); >         if (PTR_ERR(new_realm) == -EAGAIN) { >                 up_read(&mdsc->snap_rwsem); > -               if (old_realm) > +               if (!IS_ERR_OR_NULL(old_realm)) >                         ceph_put_snap_realm(mdsc, old_realm); >                 goto restart; >         } > -       is_same = (old_realm == new_realm); >         up_read(&mdsc->snap_rwsem); > > -       if (old_realm) > +       if (IS_ERR(new_realm)) > +               is_same = false; > +       else > +               is_same = (old_realm == new_realm); > + > +       if (!IS_ERR_OR_NULL(old_realm)) >                 ceph_put_snap_realm(mdsc, old_realm); > -       if (new_realm) > +       if (!IS_ERR_OR_NULL(new_realm)) >                 ceph_put_snap_realm(mdsc, new_realm); > >         return is_same; > If we just to fix the smatch check, how about make get_quota_realm() to return a 'int' type value and at the same time add a 'realmp' parameter ?  And just return '-EAGAIN' or '0' always. Then it will be something likes: diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c index c4b2929c6a83..f37f5324b6a1 100644 --- a/fs/ceph/quota.c +++ b/fs/ceph/quota.c @@ -211,10 +211,9 @@ void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)   * this function will return -EAGAIN; otherwise, the snaprealms walk-through   * will be restarted.   */ -static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc, -                                              struct inode *inode, -                                              enum quota_get_realm which_quota, -                                              bool retry) +static int get_quota_realm(struct ceph_mds_client *mdsc, struct inode *inode, +                          enum quota_get_realm which_quota, +                          struct ceph_snap_realm **realmp, bool retry)  {         struct ceph_client *cl = mdsc->fsc->client;         struct ceph_inode_info *ci = NULL; @@ -222,8 +221,10 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,         struct inode *in;         bool has_quota; +       if (realmp) +               *realmp = NULL;         if (ceph_snap(inode) != CEPH_NOSNAP) -               return NULL; +               return 0;  restart:         realm = ceph_inode(inode)->i_snap_realm; @@ -250,7 +251,7 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,                                 break;                         ceph_put_snap_realm(mdsc, realm);                         if (!retry) -                               return ERR_PTR(-EAGAIN); +                               return -EAGAIN;                         goto restart;                 } @@ -259,8 +260,11 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,                 iput(in);                 next = realm->parent; -               if (has_quota || !next) -                      return realm; +               if (has_quota || !next) { +                       if (realmp) +                               *realmp = realm; +                      return 0; +               }                 ceph_get_snap_realm(mdsc, next);                 ceph_put_snap_realm(mdsc, realm); @@ -269,14 +273,15 @@ static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,         if (realm)                 ceph_put_snap_realm(mdsc, realm); -       return NULL; +       return 0;  }  bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)  {         struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(old->i_sb); -       struct ceph_snap_realm *old_realm, *new_realm; +       struct ceph_snap_realm *old_realm = NULL, *new_realm = NULL;         bool is_same; +       int ret;  restart:         /* @@ -286,9 +291,9 @@ bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)          * dropped and we can then restart the whole operation.          */         down_read(&mdsc->snap_rwsem); -       old_realm = get_quota_realm(mdsc, old, QUOTA_GET_ANY, true); -       new_realm = get_quota_realm(mdsc, new, QUOTA_GET_ANY, false); -       if (PTR_ERR(new_realm) == -EAGAIN) { +       get_quota_realm(mdsc, old, QUOTA_GET_ANY, &old_relam, true); +       ret = get_quota_realm(mdsc, new, QUOTA_GET_ANY, &new_realm, false); +       if (ret == -EAGAIN) {                 up_read(&mdsc->snap_rwsem);                 if (old_realm)                         ceph_put_snap_realm(mdsc, old_realm); Won't be this better ? Thanks - Xiubo > >> Thanks >> >> - Xiubo >> >> >>> Thanks >>> >>>> Thanks >>>> >>>> - Xiubo >>>> >>>> >>>>> Thanks, >>>>> >>>>>                  Ilya >>>>> >>>> >>> >> >> >