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SubjectRe: [PATCH] ceph: quota: Fix invalid pointer access in
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On 2023/11/17 14:14, Xiubo Li wrote:
>
> 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 <xiubli@redhat.com> wrote:
>>>>>>>
>>>>>>> On 11/15/23 20:32, Ilya Dryomov wrote:
>>>>>>>> On Wed, Nov 15, 2023 at 1:35 AM Xiubo Li <xiubli@redhat.com> 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@huawei.com>
>>>>>>>>>> ---
>>>>>>>>>>     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@redhat.com>
>>>>>>>>>
>>>>>>>>> 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 ?
>

Yes, it looks better.

Would you post a patch to address it? Or should I apply your changes and
send a V2?

> Thanks
>
> - Xiubo
>
>
>
>
>>
>>> Thanks
>>>
>>> - Xiubo
>>>
>>>
>>>> Thanks
>>>>
>>>>> Thanks
>>>>>
>>>>> - Xiubo
>>>>>
>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>                  Ilya
>>>>>>
>>>>>
>>>>
>>>
>>>
>>
>

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