From: santosh.shilimkar@oracle.com
To: zerons <sironhide0null@gmail.com>
Cc: netdev <netdev@vger.kernel.org>,
OFED mailing list <linux-rdma@vger.kernel.org>
Subject: Re: Maybe a race condition in net/rds/rdma.c?
Date: Thu, 27 Feb 2020 10:10:53 -0800 [thread overview]
Message-ID: <94b20d30-1d7d-7a66-b943-d75a05bcb46e@oracle.com> (raw)
In-Reply-To: <D8EB4A77-77D7-41EB-9021-EA7BB8C3FA5B@oracle.com>
>> 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
next parent reply other threads:[~2020-02-27 18:10 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 ` santosh.shilimkar [this message]
2020-03-06 12:11 ` Maybe a race condition in net/rds/rdma.c? zerons
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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