linux-kernel - Re: [syzbot] [usb?] WARNING in dib0700_i2c_xfer/usb_submit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6bb3b80b-a808-4992-8666-535ed9a5c980@rowland.harvard.edu>
Date: Tue, 25 Mar 2025 13:47:15 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	syzbot <syzbot+c38e5e60d0041a99dbf5@...kaller.appspotmail.com>,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, syzkaller-bugs@...glegroups.com,
	linux-i2c@...r.kernel.org
Subject: Re: [syzbot] [usb?] WARNING in dib0700_i2c_xfer/usb_submit_urb

On Tue, Mar 25, 2025 at 05:59:10PM +0100, Wolfram Sang wrote:
> 
> > > > As far as I can tell from the source code, the dib0700 simply isn't able 
> > > > to handle 0-length reads.  Should the dib0700_ctrl_rd() routine be 
> > > > changed simply to return 0 in such cases?
> > > 
> > > The adapter (I assume the one in dvb-usb-i2c.c) should populate an
> > > i2c_adapter_quirks struct with I2C_AQ_NO_ZERO_LEN and then the core will
> > > bail out for you.
> > 
> > Or the I2C_AQ_NO_ZERO_LEN_READ flag bit.
> 
> Yes, that would be more convervative. Does USB allow zero-length writes?

It does.

> > What about all the other fields in the i2c_adapter_quirks structure?  
> > How should they be set?  (Note: I don't know anything about this driver 
> > or these devices; I'm just chasing down the syzbot bug report.)
> 
> As I also don't know the hardware, I suggest to leave them empty. 0
> means "no quirk".

Okay, let's see if this works.

Alan Stern


#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5fc319360819

Index: usb-devel/drivers/media/usb/dvb-usb/dvb-usb-i2c.c
===================================================================
--- usb-devel.orig/drivers/media/usb/dvb-usb/dvb-usb-i2c.c
+++ usb-devel/drivers/media/usb/dvb-usb/dvb-usb-i2c.c
@@ -10,6 +10,9 @@
 
 int dvb_usb_i2c_init(struct dvb_usb_device *d)
 {
+	static const struct i2c_adapter_quirks i2c_usb_quirks = {
+		.flags = I2C_AQ_NO_ZERO_LEN_READ,
+	};
 	int ret = 0;
 
 	if (!(d->props.caps & DVB_USB_IS_AN_I2C_ADAPTER))
@@ -24,6 +27,7 @@ int dvb_usb_i2c_init(struct dvb_usb_devi
 	strscpy(d->i2c_adap.name, d->desc->name, sizeof(d->i2c_adap.name));
 	d->i2c_adap.algo      = d->props.i2c_algo;
 	d->i2c_adap.algo_data = NULL;
+	d->i2c_adap.quirks    = &i2c_usb_quirks;
 	d->i2c_adap.dev.parent = &d->udev->dev;
 
 	i2c_set_adapdata(&d->i2c_adap, d);