From: Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: "Hefty,
Sean" <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Jason Gunthorpe
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH] IB/ucma: Fix theoretical user triggered use-after-free
Date: Fri, 14 Aug 2015 21:22:25 -0400 [thread overview]
Message-ID: <55CE9451.3040803@redhat.com> (raw)
In-Reply-To: <1828884A29C6694DAF28B7E6B8A82373A9023323-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
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On 08/06/2015 01:33 PM, Hefty, Sean wrote:
>> Something like this:
>>
>> CPU A CPU B
>> ======================== ================================
>> ucma_destroy_id()
>> wait_for_completion()
>> .. anything
>> ucma_put_ctx()
>> complete()
>> .. continues ...
>> ucma_leave_multicast()
>> mutex_lock(mut)
>> atomic_inc(ctx->ref)
>> mutex_unlock(mut)
>> ucma_free_ctx()
>> ucma_cleanup_multicast()
>> mutex_lock(mut)
>> kfree(mc)
>> rdma_leave_multicast(mc->ctx->cm_id,..
>>
>> Fix it by latching the ref at 0. Once it goes to 0 mc and ctx cannot
>> leave the mutex(mut) protection.
>>
>> The other atomic_inc in ucma_get_ctx is OK because mutex(mut) protects
>> it from racing with ucma_destroy_id.
>>
>> Signed-off-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
>
> Acked-by: Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
This has been picked up. Thanks.
--
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
GPG KeyID: 0E572FDD
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prev parent reply other threads:[~2015-08-15 1:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-04 23:13 [PATCH] IB/ucma: Fix theoretical user triggered use-after-free Jason Gunthorpe
[not found] ` <20150804231332.GA22959-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-08-06 17:33 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A9023323-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-08-15 1:22 ` Doug Ledford [this message]
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