Re: [PATCH -next] drm/amdkfd: Fix NULL pointer dereference in svm_migrate_to_ram()

[Felix Kuehling <felix.kuehling@amd.com>]

Am 2022-10-25 um 03:28 schrieb Yang Li:
> ./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@linux.alibaba.com>
> Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index cddf259875c0..405dd51521dc 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -981,7 +981,8 @@ static vm_fault_t svm_migrate_to_ram(struct vm_fault *vmf)
>   out_mmput:
>   	mmput(mm);
>   
> -	pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);
> +	if (p)
> +		pr_debug("CPU fault svms 0x%p address 0x%lx done\n", &p->svms, addr);

Thank you for catching and reporting this problem. I think the correct 
solution would be to move the pr_debug up before the kfd_unref_process 
call. That way you're sure that the pointer is initialized and that it 
represents a valid reference to the kfd_process structure.

Regards,
   Felix


>   
>   	return r ? VM_FAULT_SIGBUS : 0;
>   }