linux-kernel - Re: [RFC PATCH 1/1] drm/amdgpu: Fix null-ptr-deref in amdgpu_device_fini

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Date:   Fri, 30 Sep 2022 18:38:41 -0400
From:   Steven J Abner <pheonix.sja@....net>
To:     Zhang Boyang <zhangboyang.id@...il.com>
Cc:     Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Christian König <christian.koenig@....com>,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        "David C . Rankin" <drankinatty@...denlinkmail.com>
Subject: Re: [RFC PATCH 1/1] drm/amdgpu: Fix null-ptr-deref in
 amdgpu_device_fini_sw()

I had done more delving into this also, thankfully was not forgotten.
Additional info to solve blackout, was going to contact AMD:
The problem as far as I could trace occurs in amdgpu_psp.c in function 
psp_cmd_submit_buf().
Normal counter 'timeout' seems to use a max of about 400 with 
usleep_range(5, 80).
Under normal operation 'psp->fence_buf' will equal 'index' and drop 
from loop. I could not track what
fills the kernel buffer objects 'virtual' pointer's reference 
(psp->fence_buf). I assume that
it's to a firmware file that on read is returning an error, and getting 
stuck in a loop lock.
The error condition I found occurs when 'psp->fence_buf' does not equal 
'index',
breaking from loop with 'timeout' == 0.
Blackout seemed to be about 80% of reboots, but found that in 
reconfiguration of kernel,
on 5.18.19, with CONFIG_ATA_ACPI=y drops blackouts to about 30% of 
reboots. I have now avoided
all blackouts with addition of CONFIG_SATA_PMP=y (at least a week 
free?).
This is pure guess but, maybe the ARM PSP processor is dependent on 
libata procedures, one
of which causes a lock up some of the time.
Steve

On Fri, Sep 30, 2022 at 21:41, Zhang Boyang <zhangboyang.id@...il.com> 
wrote:
> After amdgpu_device_init() failed, adev->reset_domain may be NULL. 
> Thus
> subsequent call to amdgpu_device_fini_sw() may result in 
> null-ptr-deref.
> 
> This patch fixes the problem by adding a NULL pointer check around the
> code of releasing adev->reset_domain in amdgpu_device_fini_sw().
> 
> Fixes: cfbb6b004744 ("drm/amdgpu: Rework reset domain to be 
> refcounted.")
> 
> Signed-off-by: Zhang Boyang <zhangboyang.id@...il.com>
> Link: 
> https://lore.kernel.org/lkml/a8bce489-8ccc-aa95-3de6-f854e03ad557@suddenlinkmail.com/
> Link: https://lore.kernel.org/lkml/AT9WHR.3Z1T3VI9A2AQ3@att.net/
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index be7aff2d4a57..204daad06b32 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4021,8 +4021,10 @@ void amdgpu_device_fini_sw(struct 
> amdgpu_device *adev)
>  	if (adev->mman.discovery_bin)
>  		amdgpu_discovery_fini(adev);
> 
> -	amdgpu_reset_put_reset_domain(adev->reset_domain);
> -	adev->reset_domain = NULL;
> +	if (adev->reset_domain) {
> +		amdgpu_reset_put_reset_domain(adev->reset_domain);
> +		adev->reset_domain = NULL;
> +	}
> 
>  	kfree(adev->pci_state);
> 
> --
> 2.30.2
>