Re: Patch "fanotify: Release SRCU lock when waiting for userspace response" has been added to the 4.9-stable tree

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On Fri, Apr 12, 2019 at 10:44:12AM +0200, Jan Kara wrote:
On Thu 11-04-19 11:26:27, Sasha Levin wrote:
This is a note to let you know that I've just added the patch titled

    fanotify: Release SRCU lock when waiting for userspace response

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fanotify-release-srcu-lock-when-waiting-for-userspac.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.

I'd be careful with this series. You're missing at least the fixup series
from Miklos culminating in f37650f1c7c7 "fanotify: fix
fsnotify_prepare_user_wait() failure". And you seem to be missing also
quite some prerequisites reworking lifetime of fsnotify marks (series
culminating with f09b04a03e0 "fsnotify: Remove special handling of mark
destruction on group shutdown"). So you're just introducing subtle
use-after-free issues to fanotify code. Overall I think the chances for
regressions here are much bigger than the problem you'll be fixing unless
you'll go for something like wholesale update of fs/notify/* to state in
f37650f1c7c7.

I've pulled this series based on the request here:
https://lore.kernel.org/stable/20190411032430.17353-1-matthew.ruffell@xxxxxxxxxxxxx/

There are a few reasons why I'd prefer to keep it in:

1. It fixes a very real bug which has affected quite a few of our
customers as well, so (at least for me) this is more than a minor
bugfix.

2. It came with a straightforward testcase.

3. Given that Canonical pulled it in as well, it (hopefully) received
more testing than some other random patches.


If there are missing patches here I'd be happy to take them in and
re-test the kernel, but I'd really like to avoid *not* taking these
patches just because we fear a regression but can't show it.


--
Thanks,
Sasha




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