linux-kernel - Re: [PATCH] virt: acrn: fix a memory leak bug in acrn_dev

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Date:   Tue, 4 Jan 2022 10:47:29 +0800
From:   Li Fei1 <fei1.li@...el.com>
To:     Zhou Qingyang <zhou1615@....edu>
Cc:     kjlu@....edu, reinette.chatre@...el.com, zhi.a.wang@...el.com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        fei1.li@...el.com
Subject: Re: [PATCH] virt: acrn: fix a memory leak bug in acrn_dev_ioctl()

On Tue, Jan 04, 2022 at 10:34:39AM +0800, Zhou Qingyang wrote:
> In acrn_dev_ioctl(), vm_param is not released or passed out on the 
> error path of "if ((vm_param->reserved0 | vm_param->reserved1) != 0)", 
> which could lead to a memory leak.
> 
> Fix this bug by adding a kfree of vm_param on the error path.
> 
> This bug was found by a static analyzer.
> 
> Builds with CONFIG_ACRN_GUEST=y, CONFIG_ACRN_HSM=y show no new warnings, 
> and our static analyzer no longer warns about this code.
> 
> Fixes: 9c5137aedd11 (“9c5137aedd11 virt: acrn: Introduce VM management interfaces”)
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
> The analysis employs differential checking to identify inconsistent
> security operations (e.g., checks or kfrees) between two code paths
> and confirms that the inconsistent operations are not recovered in 
> the current function or the callers, so they constitute bugs. 
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
Hi Qingyang

Thanks a lot to fix this issue. Would you please to help to fix the same issue
in ACRN_IOCTL_SET_VCPU_REGS case ?


>  drivers/virt/acrn/hsm.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
> index 5419794fccf1..205f4c637556 100644
> --- a/drivers/virt/acrn/hsm.c
> +++ b/drivers/virt/acrn/hsm.c
> @@ -136,9 +136,11 @@ static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
>  		if (IS_ERR(vm_param))
>  			return PTR_ERR(vm_param);
>  
> -		if ((vm_param->reserved0 | vm_param->reserved1) != 0)
> -			return -EINVAL;
> -
> +		if ((vm_param->reserved0 | vm_param->reserved1) != 0) {
> +			ret = -EINVAL;
> +			kfree(vm_param);
> +			break;
> +		}
>  		vm = acrn_vm_create(vm, vm_param);
>  		if (!vm) {
>  			ret = -EINVAL;
> -- 
> 2.25.1
>