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Message-ID: <edb131d8-691a-359a-09c6-a949f9dd7bf4@huawei.com>
Date: Fri, 17 Nov 2023 16:53:49 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: Xiubo Li <xiubli@...hat.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 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@...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.
>>>
>>
>> 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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