Re: [stable] locks: fix a potential use-after-free problem when wakeup a waiter

Sasha Levin
2020-03-22T01:55:08Z

On Thu, Mar 19, 2020 at 10:41:30PM -0700, Nathan Chancellor wrote:
>On Thu, Mar 19, 2020 at 07:27:56PM +0000, Ben Hutchings wrote:
>> On Thu, 2020-03-19 at 07:37 +0100, Greg Kroah-Hartman wrote:
>> > On Wed, Mar 18, 2020 at 06:29:06PM -0400, Sasha Levin wrote:
>> > > On Wed, Mar 18, 2020 at 10:09:20PM +0000, Ben Hutchings wrote:
>> > > > This commit (included in 5.6-rc5) seems to be needed for 5.4 and 5.5
>> > > > branches:
>> > > >
>> > > > commit 6d390e4b5d48ec03bb87e63cf0a2bff5f4e116da
>> > > > Author: yangerkun <yangerkun@huawei.com>
>> > > > Date: Wed Mar 4 15:25:56 2020 +0800
>> > > >
>> > > > locks: fix a potential use-after-free problem when wakeup a waiter
>> > >
>> > > I've queued it up for 5.5 and 5.4, thanks!
>> > >
>> > > > I'm a bit surprised that it hasn't yet been applied, while some fixes
>> > > > from 5.6-rc6 have.
>> > >
>> > > Greg, I wonder if it makes sense to have you push a "Greg is here
>> > > --->" "bookmark" in the form of a tag/branch on linux-stable-rc.git? at
>> > > the very least it'll make it easy to see if something was missed or
>> > > still waiting in the queue.
>> >
>> > To quote Jeff Layton:
>> >
>> > Hi Greg, there is a performance regression with this patch. We're
>> > sorting through potential ways to address it at the moment, but you may
>> > want to hold off until we have a fix for that merged.
>> >
>> > Sorry for the hassle!
>> >
>> > Which is why I dropped it for now.
>> >
>> > I'll go drop it again :)
>>
>> I didn't see any mention of this on the stable list though.
>> I also don't think that a performance regression outweighs the
>> seriousness of the bug being fixed.
>>
>> Ben.
>>
>
>Looks like a fix for the performance regression was committed yesterday
>to mainline.
>
>dcf23ac3e846c ("locks: reinstate locks_delete_block optimization")

I've queued both 6d390e4b5d48 and dcf23ac3e846c to 5.5 and 5.4.

--
Thanks,
Sasha