Re: UBSAN whinge in ihci-hub.c

[Andrey Ryabinin]

2016-05-18 1:16 GMT+03:00 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>:
> On Tue, May 17, 2016 at 05:52:40PM -0400, Valdis Kletnieks wrote:
>> So, not content in the amount of breakage I generate already, I
>> compiled with UBSAN enabled...
>>
>> The immediately relevant part:
>>
>> [    2.418576] ================================================================================
>> [    2.418579] UBSAN: Undefined behaviour in drivers/usb/host/ehci-hub.c:877:47
>> [    2.418582] index -1 is out of range for type 'u32 [1]'
>
> <snip>
>
> It's a known bug in ubsan,

It's not a bug.  int *p = &a[-1] is undefined behavior. It doesn't
matter whether that pointer dereferenced or not.