Subject: CVE-2024-41005: netpoll: Fix race condition in netpoll_owner_active

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

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

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

netpoll: Fix race condition in netpoll_owner_active

KCSAN detected a race condition in netpoll:

	BUG: KCSAN: data-race in net_rx_action / netpoll_send_skb
	write (marked) to 0xffff8881164168b0 of 4 bytes by interrupt on cpu 10:
	net_rx_action (./include/linux/netpoll.h:90 net/core/dev.c:6712 net/core/dev.c:6822)
<snip>
	read to 0xffff8881164168b0 of 4 bytes by task 1 on cpu 2:
	netpoll_send_skb (net/core/netpoll.c:319 net/core/netpoll.c:345 net/core/netpoll.c:393)
	netpoll_send_udp (net/core/netpoll.c:?)
<snip>
	value changed: 0x0000000a -> 0xffffffff

This happens because netpoll_owner_active() needs to check if the
current CPU is the owner of the lock, touching napi->poll_owner
non atomically. The ->poll_owner field contains the current CPU holding
the lock.

Use an atomic read to check if the poll owner is the current CPU.

The Linux kernel CVE team has assigned CVE-2024-41005 to this issue.

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

	Fixed in 5.10.221 with commit 43c0ca793a18
	Fixed in 5.15.162 with commit efd29cd9c7b8
	Fixed in 6.1.96 with commit 96826b16ef9c
	Fixed in 6.6.36 with commit 3f1a155950a1
	Fixed in 6.9.7 with commit a130e7da73ae
	Fixed in 6.10 with commit c2e6a872bde9

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-2024-41005
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:
	net/core/netpoll.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/43c0ca793a18578a0f5b305dd77fcf7ed99f1265
	https://git.kernel.org/stable/c/efd29cd9c7b8369dfc7bcb34637e6bf1a188aa8e
	https://git.kernel.org/stable/c/96826b16ef9c6568d31a1f6ceaa266411a46e46c
	https://git.kernel.org/stable/c/3f1a155950a1685ffd0fd7175b3f671da8771f3d
	https://git.kernel.org/stable/c/a130e7da73ae93afdb4659842267eec734ffbd57
	https://git.kernel.org/stable/c/c2e6a872bde9912f1a7579639c5ca3adf1003916