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    SubjectRe: Status of reverted Linux patch "tty: Fix ldisc crash on reopened tty", Linux 4.9 kernel frequent crashes
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    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.

    >
    > > 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.

    Mikey

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