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Bug 1604217 - (CVE-2018-9422) CVE-2018-9422 kernel: Elevation of Privilege in futex
CVE-2018-9422 kernel: Elevation of Privilege in futex
Status: CLOSED NOTABUG
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
unspecified Severity unspecified
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Assigned To: Red Hat Product Security
impact=none,public=20160209,reported=...
: Security
Depends On:
Blocks: 1604228
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Reported: 2018-07-19 17:35 EDT by Laura Pardo
Modified: 2018-08-12 21:07 EDT (History)
50 users (show)

See Also:
Fixed In Version: kernel 4.6-rc1
Doc Type: If docs needed, set a value
Doc Text:
Non-optimized code for key handling of shared futexes was found in the Linux kernel in the form of unbounded contention time due to the page lock for real-time users. Before the fix, the page lock was an unnecessarily heavy lock for the futex path that protected too much. After the fix, the page lock is only required in a specific corner case.
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Environment:
Last Closed: 2018-08-02 07:45:10 EDT
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
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Description Laura Pardo 2018-07-19 17:35:28 EDT 
An unoptimized code of key handling for shared futexes was found in the Linux kernel in the form of unbounded contention time due to the page lock for real-time users. Before the fix the page lock was a heavy unnecessary lock for the futex path that protected too much. After the fix the page lock is only required in a specific corner case.

References:

https://source.android.com/security/bulletin/2018-07-01

https://marc.info/?w=2&r=1&s=futex%3A+Remove+requirement+for+lock_page&q=t (the discussions)

https://lore.kernel.org/patchwork/patch/645516/

Upstream patches:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=65d8fc777f6dcfee12785c057a6b57f679641c90

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=48fb6f4db940e92cfb16cd878cddd59ea6120d06
Comment 3 Vladis Dronov 2018-08-02 07:45:10 EDT 
Notes:

It does not look like this flaw can be exploited and even if it is really a security flaw at all. Probably, there is a confusion about the commit messages as it mentions "one rare race". Actually no race was addressed by the commit but the commit message could be interpreted so, as fixing a race related to shmem pages and a swapcache.
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