c64396cc36
- Address a longstanding issue where the user space part of the PI futex
is not writeable. The kernel returns with inconsistent state which can
in the worst case result in a UAF of a tasks kernel stack. The solution
is to establish consistent kernel state which makes future operations
on the futex fail because user space and kernel space state are
inconsistent. Not a problem as PI futexes fundamentaly require a
functional RW mapping and if user space pulls the rug under it, then it
can keep the pieces it asked for.
- Address an issue where the return value is incorrect in case that the
futex was acquired after a timeout/signal made the waiter drop out of
the rtmutex wait. In one of the corner cases the kernel returned an
error code despite having successfully acquired the futex.
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Merge tag 'locking-urgent-2021-01-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"A set of PI futex fixes:
- Address a longstanding issue where the user space part of the PI
futex is not writeable. The kernel returns with inconsistent state
which can in the worst case result in a UAF of a tasks kernel
stack.
The solution is to establish consistent kernel state which makes
future operations on the futex fail because user space and kernel
space state are inconsistent. Not a problem as PI futexes
fundamentaly require a functional RW mapping and if user space
pulls the rug under it, then it can keep the pieces it asked for.
- Address an issue where the return value is incorrect in case that
the futex was acquired after a timeout/signal made the waiter drop
out of the rtmutex wait.
In one of the corner cases the kernel returned an error code
despite having successfully acquired the futex"
* tag 'locking-urgent-2021-01-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Handle faults correctly for PI futexes
futex: Simplify fixup_pi_state_owner()
futex: Use pi_state_update_owner() in put_pi_state()
rtmutex: Remove unused argument from rt_mutex_proxy_unlock()
futex: Provide and use pi_state_update_owner()
futex: Replace pointless printk in fixup_owner()
futex: Ensure the correct return value from futex_lock_pi()
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.