From: Sasha Levin <sashal@kernel.org>
To: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: stable@vger.kernel.org
Subject: Re: [PATCH 4.4 0/5] fanotify: Fix notification subsystem hang
Date: Wed, 10 Apr 2019 12:44:18 -0400 [thread overview]
Message-ID: <20190410164418.GD11568@sasha-vm> (raw)
In-Reply-To: <20190410045456.23298-1-matthew.ruffell@canonical.com>
On Wed, Apr 10, 2019 at 04:54:51PM +1200, Matthew Ruffell wrote:
>BugLink: https://bugs.launchpad.net/bugs/1775165
>
>[Note to upstream]
>I understand that this patch is a little long for -stable, but this patch series
>fixes a real issue, seen by real users, is testable, and is made up from
>upstream commits. Please consider it.
>
>[Impact]
>
>When userspace tasks which are processing fanotify permission events act
>incorrectly, the fsnotify_mark_srcu SRCU is held indefinitely which causes
>the whole notification subsystem to hang.
>
>This has been seen in production, and it can also be seen when running the
>Linux Test Project testsuite, specifically fanotify07.
>
>[Fix]
>
>Instead of holding the SRCU lock while waiting for userspace to respond,
>which may never happen, or not in the order we are expecting, we drop the
>fsnotify_mark_srcu SRCU lock before waiting for userspace response, and then
>reacquire the lock again when userspace responds.
>
>The fixes are from a series of upstream commits:
>
>05f0e38724e8449184acd8fbf0473ee5a07adc6c (cherry-pick)
>9385a84d7e1f658bb2d96ab798393e4b16268aaa (backport)
>abc77577a669f424c5d0c185b9994f2621c52aa4 (backport)
>
>The following are upstream commits necessary for the fixes to function:
>
>35e481761cdc688dbee0ef552a13f49af8eba6cc (backport)
>0918f1c309b86301605650c836ddd2021d311ae2 (cherry-pick)
This would also make sense for 4.9, right? I don't want to fix 4.4
without fixing 4.9 as well.
--
Thanks,
Sasha
next prev parent reply other threads:[~2019-04-10 16:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 4:54 [PATCH 4.4 0/5] fanotify: Fix notification subsystem hang Matthew Ruffell
2019-04-10 4:54 ` [PATCH 4.4 1/5] fsnotify: turn fsnotify reaper thread into a workqueue job Matthew Ruffell
2019-04-10 4:54 ` [PATCH 4.4 2/5] fsnotify: avoid spurious EMFILE errors from inotify_init() Matthew Ruffell
2019-04-10 4:54 ` [PATCH 4.4 3/5] fsnotify: Provide framework for dropping SRCU lock in ->handle_event Matthew Ruffell
2019-04-10 4:54 ` [PATCH 4.4 4/5] fsnotify: Pass fsnotify_iter_info into handle_event handler Matthew Ruffell
2019-04-10 4:54 ` [PATCH 4.4 5/5] fanotify: Release SRCU lock when waiting for userspace response Matthew Ruffell
2019-04-10 16:44 ` Sasha Levin [this message]
2019-04-11 3:54 ` [PATCH 4.4 0/5] fanotify: Fix notification subsystem hang Matthew Ruffell
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