linux-kernel - Re: [PATCH -next] drm/amdkfd: Fix NULL pointer dereference in svm_migrate_to

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Date:   Wed, 26 Oct 2022 16:37:47 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     Yang Li <yang.lee@...ux.alibaba.com>, alexander.deucher@....com
Cc:     christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Abaci Robot <abaci@...ux.alibaba.com>
Subject: Re: [PATCH -next] drm/amdkfd: Fix NULL pointer dereference in
 svm_migrate_to_ram()

On 2022-10-25 22:00, Yang Li wrote:
> ./drivers/gpu/drm/amd/amdkfd/kfd_migrate.c:985:58-62: ERROR: p is NULL but dereferenced.
>
> Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2549
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>

The patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>

I applied to our amd-staging-drm-next branch.

Thanks,
   Felix


> ---
>
> change in v2:
> According to Felix's suggestion, move the pr_debug up before the kfd_unref_process
> call.
>
>   drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index 20d6b2578927..b9c8d29d95aa 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -978,12 +978,10 @@ static vm_fault_t svm_migrate_to_ram(struct vm_fault *vmf)
>   out_unlock_svms:
>   	mutex_unlock(&p->svms.lock);
>   out_unref_process:
> +	pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
>   	kfd_unref_process(p);
>   out_mmput:
>   	mmput(mm);
> -
> -	pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
> -
>   	return r ? VM_FAULT_SIGBUS : 0;
>   }
>