Re: [Patch] gutenprint53+usb crashes with libusb-1.0.25

Hi Solomon,

thank you for looking into the issue!

On 2/22/22 19:00, Solomon Peachy wrote:
> On Tue, Feb 22, 2022 at 07:55:18AM +0100, Zdenek Dohnal wrote:
>> there were changes in libusb 1.0.25 which is in Fedora 36 - f.e. default USB
>> context is not initialized unless you specifically pass NULL into
>> `libusb_init()` - gutenprint53+usb backend actually depended on this hidden
>> behavior, because it passes its own context address into `libusb_init()`
>> instead of NULL. So the change causes the backend to crash if you run it:
> Yikes!
>
>> According libusb maintainer, Ben Berg, the backend can work with the default
>> USB context and he prepared the patch for it (the file is attached). I was
>> able to verify the patch fixes the crash, but I don't have a device
>> supported by gutenprint itself, so I couldn't do an additional sanity
>> testing. The patch looks good to me though.
> Will this work for multi-threaded stuff where there could conceivably be
> multiple contexts in use?  That's not being exercised in the current
> gutenprint code but some of the stuff I have cooking will change that.

Ben, would you mind looking into it? IMO we probably cannot use a 
default USB context for multi-threading...

In such case, IMO we can init the default context just for the 
print_help() scope and close it after we're done with it.

You can join us in discussion on the bug if you are able as well [1], 
I've pinged Robert there as well, because I didn't know your email for 
bugzilla...

>
>> Would you mind adding the patch to the project if it looks good for you?
> I won't be able to physically test any of this until this coming weekend
> (out of town and while I have remote access everything pertinent is
> turned off) but when I'm back, I'll be able to at least it doesn't
> introduce any regressions on F34 & F35.
Ok, Ben reverted the libusb change for now to do not block Fedora 36 
beta, so IMO after weekend is fine :) .
>
>   - Solomon


[1] https://bugzilla.redhat.com/show_bug.cgi?id=2055504

-- 
Zdenek Dohnal
Software Engineer
Red Hat, BRQ-TPBC