linux-kernel - Re: [syzbot] memory leak in usb_get

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Date:   Thu, 10 Mar 2022 10:29:02 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     syzbot <syzbot+f0fae482604e6d9a87c9@...kaller.appspotmail.com>,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, pavel.hofman@...tera.com,
        rob@...greener.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] memory leak in usb_get_configuration

On Thu, Mar 10, 2022 at 10:51:42AM +0100, Oliver Neukum wrote:
> 
> On 10.03.22 00:54, syzbot wrote:
> 
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    0014404f9c18 Merge branch 'akpm' (patches from Andrew)
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15864216700000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3f0a704147ec8e32
> > dashboard link: https://syzkaller.appspot.com/bug?extid=f0fae482604e6d9a87c9
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13a63dbe700000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e150a1700000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+f0fae482604e6d9a87c9@...kaller.appspotmail.com
> >
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 0014404f9c18
> 
>  

> From 785609ab0d95c753dc31267b3c4da585c16e0274 Mon Sep 17 00:00:00 2001
> From: Oliver Neukum <oneukum@...e.com>
> Date: Thu, 10 Mar 2022 10:40:36 +0100
> Subject: [PATCH] USB: hub: fix memory leak on failure of usb_get_config
> 
> kfree()s on the error path need to be added.

No, they don't.  The config and rawdescriptors buffers get freed later 
on in usb_destroy_configuration().

This problem is something else.  Probably whatever driver is calling 
gspca_probe() (see the console log) is taking a reference to the 
usb_device or usb_interface and then failing to release that reference 
on its error path.

Alan Stern

> Signed-off-by: Oliver Neukum <oneukum@...e.com>
> ---
>  drivers/usb/core/config.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 48bc8a4814ac..548ce5ca6847 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -885,12 +885,16 @@ int usb_get_configuration(struct usb_device *dev)
>  
>  	length = ncfg * sizeof(char *);
>  	dev->rawdescriptors = kzalloc(length, GFP_KERNEL);
> -	if (!dev->rawdescriptors)
> -		return -ENOMEM;
> +	if (!dev->rawdescriptors) {
> +		result = -ENOMEM;
> +		goto err2;
> +	}
>  
>  	desc = kmalloc(USB_DT_CONFIG_SIZE, GFP_KERNEL);
> -	if (!desc)
> -		return -ENOMEM;
> +	if (!desc) {
> +		result = -ENOMEM;
> +		goto err2;
> +	}
>  
>  	for (cfgno = 0; cfgno < ncfg; cfgno++) {
>  		/* We grab just the first descriptor so we know how long
> @@ -952,6 +956,11 @@ int usb_get_configuration(struct usb_device *dev)
>  err:
>  	kfree(desc);
>  	dev->descriptor.bNumConfigurations = cfgno;
> +err2:
> +	kfree(dev->rawdescriptors);
> +	kfree(dev->config);
> +	dev->rawdescriptors = NULL;
> +	dev->config = NULL;
>  
>  	return result;
>  }
> -- 
> 2.34.1
>