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Date: Fri, 17 Nov 2023 14:14:31 +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 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 ?
Thanks
- Xiubo
>
>> Thanks
>>
>> - Xiubo
>>
>>
>>> Thanks
>>>
>>>> Thanks
>>>>
>>>> - Xiubo
>>>>
>>>>
>>>>> Thanks,
>>>>>
>>>>> Ilya
>>>>>
>>>>
>>>
>>
>>
>
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