linux-kernel - Re: [PATCH] mm: memory_hotplug: fix memory error handling

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Message-ID: <0563a019-09e3-a176-d4c1-c240f3cf62d0@redhat.com>
Date:   Mon, 30 May 2022 08:55:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Muchun Song <songmuchun@...edance.com>, gregkh@...uxfoundation.org,
        rafael@...nel.org, cheloha@...ux.vnet.ibm.com, mhocko@...e.com,
        akpm@...ux-foundation.org, nathanl@...ux.ibm.com
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] mm: memory_hotplug: fix memory error handling

On 30.05.22 07:33, Muchun Song wrote:
> The device_unregister() is supposed to be used to unregister devices if
> device_register() has succeed.  And device_unregister() will put device.
> The caller should not do it again, otherwise, the first call of
> put_device() will drop the last reference count, then the next call
> of device_unregister() will UAF on device.
> 
> Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> Cc: <stable@...r.kernel.org>
> ---
>  drivers/base/memory.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 7222ff9b5e05..084d67fd55cc 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
>  	}
>  	ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
>  			      GFP_KERNEL));
> -	if (ret) {
> -		put_device(&memory->dev);
> +	if (ret)
>  		device_unregister(&memory->dev);
> -	}
> +
>  	return ret;
>  }
>  

See

https://lkml.kernel.org/r/d44c63d78affe844f020dc02ad6af29abc448fc4.1650611702.git.christophe.jaillet@wanadoo.fr

-- 
Thanks,

David / dhildenb