virt September 2017

virt@lists.centos.org

14 participants
11 discussions

Re: [CentOS-virt] Status of reverted Linux patch "tty: Fix ldisc crash on reopened tty", Linux 4.9 kernel frequent crashes
by Pasi Kärkkäinen 01 Sep '17

01 Sep '17

On Thu, Aug 31, 2017 at 03:22:05PM +1000, Michael Neuling wrote: > On Thu, 2017-08-31 at 06:36 +0200, Greg Kroah-Hartman wrote: > > On Wed, Aug 30, 2017 at 11:10:14PM +0300, Pasi Kärkkäinen wrote: > > > Hello everyone, > > > > > > Recently Nathan March reported on centos-virt list he's getting frequent > > > Linux kernel crashes with Linux 4.9 LTS kernel because of the missing patch > > > "tty: Fix ldisc crash on reopened tty". > > > > Crashes with "normal" operation, or crashes when running a fuzzer or > > other type of program? > > For me it crashed on boot. > Nathan said he's getting the crashes at runtime, randomly, but often. > > > > > The patch was already merged upstream here: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i > > > d=71472fa9c52b1da27663c275d416d8654b905f05 > > > > > > but then reverted here: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i > > > d=896d81fefe5d1919537db2c2150ab6384e4a6610 > > > > > > Nathan confirmed if he applies the patch from > > > 71472fa9c52b1da27663c275d416d8654b905f05 to his Linux 4.9 LTS kernel the > > > bug/problem goes away, so the patch (or similar fix) is still needed, at > > > least for 4.9 LTS kernel. > > > > > > > > > Mikulas reported he's able to trigger the same crash on Linux 4.10: > > > https://www.spinics.net/lists/kernel/msg2440637.html > > > https://lists.gt.net/linux/kernel/2664604?search_string=ldisc%20reopened;#26 > > > 64604 > > > > > > Michael Neuling reported he's able to trigger the bug on PowerPC: > > > https://lkml.org/lkml/2017/3/10/1582 > > > > > > > > > So now the question is.. is anyone currently working on getting this patch > > > fixed and applied upstream? I think one of the problems earlier was being > > > able to reliable reproduce the crash.. Nathan says he's able to reproduce it > > > many times per week on his environment on x86_64. > > > > I don't know of anyone working on it, want to do it yourself? > > I'm not anymore. We found it was only triggered on a bogus CONFIG option > combination. Once we removed that, it no longer happened. > > The underlying bug was still there though. > Yep.. and the bug seems to trigger at runtime. > Mikey -- Pasi

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virt September 2017