From: Petr Cvek <petrcvekcz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Jason Gunthorpe <jgg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Cc: "Deucher,
Alexander" <Alexander.Deucher-5C7GfCeVMHo@public.gmane.org>,
"David1.Zhou-5C7GfCeVMHo@public.gmane.org"
<David1.Zhou-5C7GfCeVMHo@public.gmane.org>,
"Koenig,
Christian" <christian.koenig-5C7GfCeVMHo@public.gmane.org>,
"amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
<amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>,
"sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org"
<sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>
Subject: Re: [BUG, regression] Dereferencing of NULL pointer in radeon_mn_unregister()
Date: Sun, 1 Sep 2019 17:48:36 +0200 [thread overview]
Message-ID: <2fc7ef14-e89a-1f2d-381d-1c9b05da02d3@gmail.com> (raw)
In-Reply-To: <20190901140409.GA1251-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Dne 01. 09. 19 v 16:04 Jason Gunthorpe napsal(a):
> On Sun, Sep 01, 2019 at 11:38:10AM +0200, Petr Cvek wrote:
>
>> The code is:
>>
>> struct radeon_mn *rmn = bo->mn;
>> ...
>> mutex_lock(&rmn->lock); //<-crash
>>
>> A quick assert proves the bo->mn returns NULL. The code worked in
>> 4.19-rc and it seems the problematic patch is
>
> Hum, the code went away because the locking protecting that variable
> went away.. It means the caller is not careful to pair register and
> unregister.
>
>> drm/radeon: use mmu_notifier_get/put for struct radeon_mn
>>
>> as it removes the NULL check.
>>
>> Forcing -ENODEV in the register funtion (and immediate return in
>> unregister as without CONFIG_MMU_NOTIFIER) works.
>
> Is just adding a
>
> if (!rmn)
> retrun
>
> To the top of radeon_mn_unregister enough to fix it?
Yeah it seems to work. A further test with minetest works too.
Petr
>
> Jason
>
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next prev parent reply other threads:[~2019-09-01 15:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-01 9:38 [BUG, regression] Dereferencing of NULL pointer in radeon_mn_unregister() Petr Cvek
[not found] ` <dad0e51a-0f06-e2b0-cef7-3587207c2045-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2019-09-01 14:04 ` Jason Gunthorpe
[not found] ` <20190901140409.GA1251-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2019-09-01 15:48 ` Petr Cvek [this message]
[not found] ` <2fc7ef14-e89a-1f2d-381d-1c9b05da02d3-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2019-09-02 6:19 ` Jason Gunthorpe
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