linux-kernel - Re: [PATCH v2] staging: rtl8192u: add error handling for usb_alloc

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Message-ID: <CAGXu5jJbwAZxCYMF=j2XQAhgKU90XaL2oRCG_sny_KBVcTJhOg@mail.gmail.com>
Date:   Fri, 15 Jun 2018 09:47:16 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Zhouyang Jia <jiazhouyang09@...il.com>, devel@...verdev.osuosl.org,
        LKML <linux-kernel@...r.kernel.org>,
        Jia-Ju Bai <baijiaju1990@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Shreeya Patel <shreeya.patel23498@...il.com>,
        Colin Ian King <colin.king@...onical.com>
Subject: Re: [PATCH v2] staging: rtl8192u: add error handling for usb_alloc_urb

On Fri, Jun 15, 2018 at 9:33 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Sat, Jun 16, 2018 at 12:25:23AM +0800, Zhouyang Jia wrote:
>> When usb_alloc_urb fails, the lack of error-handling code may
>> cause unexpected results.
>>
>> This patch adds error-handling code after calling usb_alloc_urb.
>>
>> Signed-off-by: Zhouyang Jia <jiazhouyang09@...il.com>
>> ---
>> v1->v2:
>> - Fix memory leak.
>> ---
>>  drivers/staging/rtl8192u/r8192U_core.c | 18 +++++++++++++++---
>>  1 file changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/staging/rtl8192u/r8192U_core.c b/drivers/staging/rtl8192u/r8192U_core.c
>> index 7a0dbc0..6afab4e 100644
>> --- a/drivers/staging/rtl8192u/r8192U_core.c
>> +++ b/drivers/staging/rtl8192u/r8192U_core.c
>> @@ -1648,13 +1648,17 @@ static short rtl8192_usb_initendpoints(struct net_device *dev)
>>  #ifndef JACKSON_NEW_RX
>>       for (i = 0; i < (MAX_RX_URB + 1); i++) {
>>               priv->rx_urb[i] = usb_alloc_urb(0, GFP_KERNEL);
>> -             if (!priv->rx_urb[i])
>> +             if (!priv->rx_urb[i]) {
>> +                     kfree(priv->rx_urb);

You're freeing rx_urb, which holds all the pointers to allocated
memory. You'll need to free each item of the array before freeing the
array itself:

for (i = 0; i < (MAX_RX_URB + 1); i++)
    kfree(priv->rx_urb[i]);
kfree(priv->rx_urb);

I think you need some kind of helper to do this, and you can call into
it from your error paths...

-Kees

> {sigh}
>
> No, you are still leaking memory on all of these changes that you just
> made :(
>
> greg k-h



-- 
Kees Cook
Pixel Security