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

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Date:   Wed, 15 Nov 2023 21:34:54 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Ilya Dryomov <idryomov@...il.com>
Cc:     Wenchao Hao <haowenchao2@...wei.com>,
        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 11/15/23 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 ?

Thanks

- Xiubo


> Thanks,
>
>                  Ilya
>