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

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Message-ID: <Z-Lg3glmnzA44R_H@shikoro>
Date: Tue, 25 Mar 2025 17:59:10 +0100
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: Alan Stern <stern@...land.harvard.edu>
Cc: 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


> > > 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?

> 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".


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