linux-kernel - Re: [PATCH] misc: fastrpc: Fix double free of 'buf' in error path

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Message-ID: <4aa42c38-e0e2-4d2d-bfe2-15bc151f7117@linaro.org>
Date:   Fri, 19 May 2023 11:39:59 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Sukrut Bellary <sukrut.bellary@...ux.com>,
        Abel Vesa <abel.vesa@...aro.org>,
        Amol Maheshwari <amahesh@....qualcomm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] misc: fastrpc: Fix double free of 'buf' in error path



On 19/05/2023 11:22, Dan Carpenter wrote:
>> ----------------------->cut<---------------------------
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index f60bbf99485c..3fdd326e1ae8 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -1891,7 +1891,8 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl,
>> char __user *argp)
>>                                        &args[0]);
>>          if (err) {
>>                  dev_err(dev, "mmap error (len 0x%08llx)\n", buf->size);
>> -               goto err_invoke;
>> +               fastrpc_buf_free(buf);
>> +               return err;
>>          }
>>
>>          /* update the buffer to be able to deallocate the memory on the DSP
>> */
>> @@ -1930,11 +1931,7 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl,
>> char __user *argp)
>>          return 0;
>>
>>   err_assign:
>> -       fastrpc_req_munmap_impl(fl, buf);
>> -err_invoke:
>> -       fastrpc_buf_free(buf);
>> -
>> -       return err;
>> +       return fastrpc_req_munmap_impl(fl, buf);
> 
> This will return success if copy_to_user() fails.
> 
that is true, using return value of fastrpc_req_munmap_impl does not 
really make sense here we should just return err in either case to the user.

--srini

> regards,
> dan carpenter
>