linux-kernel - Re: [PATCH RESEND] drm/lease: fix potential race in fill_object

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Message-ID: <CAJRQjofSWYR--4V_4zmp6K9WVtqShdzpGuH1VFBPvHpViGYH5g@mail.gmail.com>
Date:   Wed, 18 Mar 2020 06:33:34 +0800
From:   Qiujun Huang <hqjagain@...il.com>
To:     Qiujun Huang <hqjagain@...il.com>,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH RESEND] drm/lease: fix potential race in fill_object_idr

On Wed, Mar 18, 2020 at 1:02 AM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Mon, Mar 16, 2020 at 03:18:23PM +0800, Qiujun Huang wrote:
> > We should hold idr_mutex for idr_alloc.
> >
> > Signed-off-by: Qiujun Huang <hqjagain@...il.com>
>
> I've not seen the first version of this anywhere in my inbox, not sure
> where that got lost.
>
> Anyway, this seems like a false positive - I'm assuming this was caught
> with KCSAN. The commit message really should mention that.
>
> fill_object_idr creates the idr, which yes is only access later on under
> the idr_mutex. But here it's not yet visible to any other thread, and
> hence lockless access is safe and correct.

Agree that.
Thanks.

>
> No idea what the KCSAN complains about safe access like this best practice
> is.
> -Daniel
>