linux-kernel - Re: [PATCH] media: em28xx: fix memory leak in em28xx_init

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Date:   Mon, 1 Nov 2021 22:28:37 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Dongliang Mu <mudongliangabcd@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        syzbot <syzkaller@...glegroups.com>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: em28xx: fix memory leak in em28xx_init_dev

On 11/1/21 21:32, Dan Carpenter wrote:
> On Mon, Nov 01, 2021 at 05:55:39PM +0800, Dongliang Mu wrote:
>> In the em28xx_init_rev, if em28xx_audio_setup fails, this function fails
>> to deallocate the media_dev allocated in the em28xx_media_device_init.
>> 
>> Fix this by adding em28xx_unregister_media_device to free media_dev.
>> 
>> BTW, this patch is tested in my local syzkaller instance, and it can
>> prevent the memory leak from occurring again.
>> 
>> CC: Pavel Skripkin <paskripkin@...il.com>
>> Fixes: 37ecc7b1278f ("[media] em28xx: add media controller support")
>> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
>> Reported-by: syzbot <syzkaller@...glegroups.com>
> 
> Is this really a syzbot warning?  If so it should be in the format:
> 
> Reported-by: syzbot+4c4ffd1e1094dae61035@...kaller.appspotmail.com
> 
> Syzbot is different from syzkaller.  Syzkaller is the fuzzer and syzbot
> is the program which reports syzkaller bugs.
> 

Bug report is from his local instance. He just wants to give credit to 
syzbot for finding it

>> ---
>>  drivers/media/usb/em28xx/em28xx-cards.c | 19 +++++++++++++------
>>  1 file changed, 13 insertions(+), 6 deletions(-)
>> 
>> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
>> index c1e0dccb7408..fca68939ca50 100644
>> --- a/drivers/media/usb/em28xx/em28xx-cards.c
>> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
>> @@ -3625,8 +3625,10 @@ static int em28xx_init_dev(struct em28xx *dev, struct usb_device *udev,
>>  
> 
> There is no check to see if the em28xx_media_device_init() fails.  I

I guess, it should work, since there a lot of checks to see if this 
pointer is valid, i.e driver can work even without this pointer, AFAIK

> don't love that we call unregister() to undo the init() but it seems
> like it should work...

Same here, but it is out of scope of this patch :)



With regards,
Pavel Skripkin