From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Alan Stern <stern@rowland.harvard.edu>,
Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: <linux-kernel@vger.kernel.org>, <aryabinin@virtuozzo.com>,
<gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>
Subject: Re: UBSAN: Undefined behaviour in drivers/usb/core/devio.c:1517:25
Date: Tue, 26 Jan 2016 19:03:39 +0300 [thread overview]
Message-ID: <56A798DB.8000200@virtuozzo.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1601261023300.2062-100000@iolanthe.rowland.org>
On 01/26/2016 06:25 PM, Alan Stern wrote:
> On Tue, 26 Jan 2016, Chris Bainbridge wrote:
>
>> Booting 4.5.0-rc1 with new UBSAN checker enabled:
>>
>> [ 4.556968] ================================================================================
>> [ 4.556972] UBSAN: Undefined behaviour in drivers/usb/core/devio.c:1517:25
>> [ 4.556975] shift exponent -1 is negative
>
> Does a left shift by a negative amount matter if the result isn't used?
>
By definition, any code with undefined behavior could do anything.
But in practice, undefined shift just leads to undefined result of shift operation
(it depends on operands and architecture).
> Alan Stern
>
next prev parent reply other threads:[~2016-01-26 16:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-26 10:11 UBSAN: Undefined behaviour in drivers/usb/core/devio.c:1517:25 Chris Bainbridge
2016-01-26 15:25 ` Alan Stern
2016-01-26 16:03 ` Andrey Ryabinin [this message]
2016-01-26 16:43 ` Greg KH
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