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

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Message-ID: <6824ece2-33ee-63f4-2c7a-7033556325cb@redhat.com>
Date:   Thu, 16 Nov 2023 11:06:52 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Wenchao Hao <haowenchao2@...wei.com>,
        Ilya Dryomov <idryomov@...il.com>
Cc:     Jeff Layton <jlayton@...nel.org>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, louhongxiang@...wei.com
Subject: Re: [PATCH] ceph: quota: Fix invalid pointer access in


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@...hat.com> wrote:
>>>>
>>>> On 11/15/23 20:32, Ilya Dryomov wrote:
>>>>> On Wed, Nov 15, 2023 at 1:35 AM Xiubo Li <xiubli@...hat.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@...wei.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@...hat.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.

Thanks

- Xiubo


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