Aruna Ramakrishna 407abc7e0c x86/pkeys: Restore altstack access in sigreturn()
[ Upstream commit d10b554919d4cc8fa8fe2e95b57ad2624728c8e4 ]

A process can disable access to the alternate signal stack by not
enabling the altstack's PKEY in the PKRU register.

Nevertheless, the kernel updates the PKRU temporarily for signal
handling. However, in sigreturn(), restore_sigcontext() will restore the
PKRU to the user-defined PKRU value.

This will cause restore_altstack() to fail with a SIGSEGV as it needs read
access to the altstack which is prohibited by the user-defined PKRU value.

Fix this by restoring altstack before restoring PKRU.

Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240802061318.2140081-5-aruna.ramakrishna@oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-10-10 11:57:29 +02:00
2022-09-28 09:02:20 +02:00
2024-10-04 16:30:05 +02:00

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.
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