Bug 1604217 (CVE-2018-9422) - CVE-2018-9422 kernel: Elevation of Privilege in futex
Summary: CVE-2018-9422 kernel: Elevation of Privilege in futex
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2018-9422
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
unspecified
unspecified
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks: 1604228
TreeView+ depends on / blocked
 
Reported: 2018-07-19 21:35 UTC by Laura Pardo
Modified: 2021-09-09 15:06 UTC (History)
50 users (show)

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.
Clone Of:
Environment:
Last Closed: 2018-08-02 11:45:10 UTC


Attachments (Terms of Use)

Description Laura Pardo 2018-07-19 21:35:28 UTC
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 11:45:10 UTC
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.


Note You need to log in before you can comment on or make changes to this bug.