Subject: CVE-2024-46762: xen: privcmd: Fix possible access to a freed kirqfd instance

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

xen: privcmd: Fix possible access to a freed kirqfd instance

Nothing prevents simultaneous ioctl calls to privcmd_irqfd_assign() and
privcmd_irqfd_deassign(). If that happens, it is possible that a kirqfd
created and added to the irqfds_list by privcmd_irqfd_assign() may get
removed by another thread executing privcmd_irqfd_deassign(), while the
former is still using it after dropping the locks.

This can lead to a situation where an already freed kirqfd instance may
be accessed and cause kernel oops.

Use SRCU locking to prevent the same, as is done for the KVM
implementation for irqfds.

The Linux kernel CVE team has assigned CVE-2024-46762 to this issue.

Affected and fixed versions
===========================

	Fixed in 6.6.51 with commit e997b357b13a
	Fixed in 6.10.10 with commit 112fd2f02b30
	Fixed in 6.11 with commit 611ff1b1ae98

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-46762
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/xen/privcmd.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e997b357b13a7d95de31681fc54fcc34235fa527
	https://git.kernel.org/stable/c/112fd2f02b308564724b8e81006c254d20945c4b
	https://git.kernel.org/stable/c/611ff1b1ae989a7bcce3e2a8e132ee30e968c557