From: zerons <sironhide0null@gmail.com>
To: santosh.shilimkar@oracle.com
Cc: netdev <netdev@vger.kernel.org>,
OFED mailing list <linux-rdma@vger.kernel.org>,
haakon.bugge@oracle.com
Subject: Re: Maybe a race condition in net/rds/rdma.c?
Date: Fri, 6 Mar 2020 20:11:13 +0800 [thread overview]
Message-ID: <e525ec74-b62f-6e7c-e6bc-aad93d349f65@gmail.com> (raw)
In-Reply-To: <94b20d30-1d7d-7a66-b943-d75a05bcb46e@oracle.com>
On 2/28/20 02:10, santosh.shilimkar@oracle.com wrote:
>
>>> On 18 Feb 2020, at 14:13, zerons <sironhide0null@gmail.com> wrote:
>>>
>>> Hi, all
>>>
>>> In net/rds/rdma.c
>>> (https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/net/rds/rdma.c?h=v5.5.3*n419__;Iw!!GqivPVa7Brio!OwwQCLtjDsKmhaIz0sfaOVSuC4ai5t5_FgB7yqNExGOCBtACtIGLF61NNJyqSDtIAcGoPg$ ),
>>> there may be a race condition between rds_rdma_unuse() and rds_free_mr().
>>>
> Hmmm.. I didn't see email before in my inbox. Please post questions/patches on netdev in future which is the correct mailing list.
>
>>> It seems that this one need some specific devices to run test,
>>> unfortunately, I don't have any of these.
>>> I've already sent two emails to the maintainer for help, no response yet,
>>> (the email address may not be in use).
>>>
>>> 0) in rds_recv_incoming_exthdrs(), it calls rds_rdma_unuse() when receive an
>>> extension header with force=0, if the victim mr does not have RDS_RDMA_USE_ONCE
>>> flag set, then the mr would stay in the rbtree. Without any lock, it tries to
>>> call mr->r_trans->sync_mr().
>>>
>>> 1) in rds_free_mr(), the same mr is found, and then freed. The mr->r_refcount
>>> doesn't change while rds_mr_tree_walk().
>>>
>>> 0) back in rds_rdma_unuse(), the victim mr get used again, call
>>> mr->r_trans->sync_mr().
>>>
>>> Could this race condition actually happen?
>>>
> force=0 is an interesting scenario. Let me think about it and get back.
> Thanks for report.
>
> Regards,
> Santosh
Thanks for your attention.
Regards,
next prev parent reply other threads:[~2020-03-06 12:11 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <afd9225d-5c43-8cc7-0eed-455837b53e10@gmail.com>
[not found] ` <D8EB4A77-77D7-41EB-9021-EA7BB8C3FA5B@oracle.com>
2020-02-27 18:10 ` Maybe a race condition in net/rds/rdma.c? santosh.shilimkar
2020-03-06 12:11 ` zerons [this message]
2020-03-10 17:53 ` santosh.shilimkar
2020-03-11 4:48 ` zerons
2020-03-11 14:35 ` santosh.shilimkar
2020-03-12 8:58 ` zerons
2020-03-12 17:49 ` santosh.shilimkar
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