Subject: CVE-2024-26650: platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe

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

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

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

platform/x86: p2sb: Allow p2sb_bar() calls during PCI device probe

p2sb_bar() unhides P2SB device to get resources from the device. It
guards the operation by locking pci_rescan_remove_lock so that parallel
rescans do not find the P2SB device. However, this lock causes deadlock
when PCI bus rescan is triggered by /sys/bus/pci/rescan. The rescan
locks pci_rescan_remove_lock and probes PCI devices. When PCI devices
call p2sb_bar() during probe, it locks pci_rescan_remove_lock again.
Hence the deadlock.

To avoid the deadlock, do not lock pci_rescan_remove_lock in p2sb_bar().
Instead, do the lock at fs_initcall. Introduce p2sb_cache_resources()
for fs_initcall which gets and caches the P2SB resources. At p2sb_bar(),
refer the cache and return to the caller.

Before operating the device at P2SB DEVFN for resource cache, check
that its device class is PCI_CLASS_MEMORY_OTHER 0x0580 that PCH
specifications define. This avoids unexpected operation to other devices
at the same DEVFN.

Tested-by Klara Modin <[email-masked]>

The Linux kernel CVE team has assigned CVE-2024-26650 to this issue.

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

	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.1.76 with commit 2841631a0365
	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.6.15 with commit 847e1eb30e26
	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.7.3 with commit d281ac9a987c
	Issue introduced in 6.0 with commit 9745fb07474f and fixed in 6.8 with commit 5913320eb0b3

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-2024-26650
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/platform/x86/p2sb.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/2841631a03652f32b595c563695d0461072e0de4
	https://git.kernel.org/stable/c/847e1eb30e269a094da046c08273abe3f3361cf2
	https://git.kernel.org/stable/c/d281ac9a987c553d93211b90fd4fe97d8eca32cd
	https://git.kernel.org/stable/c/5913320eb0b3ec88158cfcb0fa5e996bf4ef681b