linux-cve-announce - CVE-2024-56610: kcsan: Turn report_filterlist_lock into a raw

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Message-ID: <2024122706-CVE-2024-56610-905f@gregkh>
Date: Fri, 27 Dec 2024 15:51:17 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-56610: kcsan: Turn report_filterlist_lock into a raw_spinlock

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

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

kcsan: Turn report_filterlist_lock into a raw_spinlock

Ran Xiaokai reports that with a KCSAN-enabled PREEMPT_RT kernel, we can see
splats like:

| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
| in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
| preempt_count: 10002, expected: 0
| RCU nest depth: 0, expected: 0
| no locks held by swapper/1/0.
| irq event stamp: 156674
| hardirqs last  enabled at (156673): [<ffffffff81130bd9>] do_idle+0x1f9/0x240
| hardirqs last disabled at (156674): [<ffffffff82254f84>] sysvec_apic_timer_interrupt+0x14/0xc0
| softirqs last  enabled at (0): [<ffffffff81099f47>] copy_process+0xfc7/0x4b60
| softirqs last disabled at (0): [<0000000000000000>] 0x0
| Preemption disabled at:
| [<ffffffff814a3e2a>] paint_ptr+0x2a/0x90
| CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.11.0+ #3
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
| Call Trace:
|  <IRQ>
|  dump_stack_lvl+0x7e/0xc0
|  dump_stack+0x1d/0x30
|  __might_resched+0x1a2/0x270
|  rt_spin_lock+0x68/0x170
|  kcsan_skip_report_debugfs+0x43/0xe0
|  print_report+0xb5/0x590
|  kcsan_report_known_origin+0x1b1/0x1d0
|  kcsan_setup_watchpoint+0x348/0x650
|  __tsan_unaligned_write1+0x16d/0x1d0
|  hrtimer_interrupt+0x3d6/0x430
|  __sysvec_apic_timer_interrupt+0xe8/0x3a0
|  sysvec_apic_timer_interrupt+0x97/0xc0
|  </IRQ>

On a detected data race, KCSAN's reporting logic checks if it should
filter the report. That list is protected by the report_filterlist_lock
*non-raw* spinlock which may sleep on RT kernels.

Since KCSAN may report data races in any context, convert it to a
raw_spinlock.

This requires being careful about when to allocate memory for the filter
list itself which can be done via KCSAN's debugfs interface. Concurrent
modification of the filter list via debugfs should be rare: the chosen
strategy is to optimistically pre-allocate memory before the critical
section and discard if unused.

The Linux kernel CVE team has assigned CVE-2024-56610 to this issue.


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

	Fixed in 5.10.231 with commit f4f2ef66d288ea796ddb8ecbdc2df074ab2d5f4d
	Fixed in 5.15.174 with commit ea6588abcc15d68fdeae777ffe3dd74c02eab407
	Fixed in 6.1.120 with commit 0ab4951c1473c7d1ceaf1232eb927109cd1c4859
	Fixed in 6.6.66 with commit dca4e74a918586913d251c0b359e8cc96a3883ea
	Fixed in 6.12.5 with commit 889a0d3a35fdedba1c5dcb6410c95c32421680ec
	Fixed in 6.13-rc1 with commit 59458fa4ddb47e7891c61b4a928d13d5f5b00aa0

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-2024-56610
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:
	kernel/kcsan/debugfs.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/f4f2ef66d288ea796ddb8ecbdc2df074ab2d5f4d
	https://git.kernel.org/stable/c/ea6588abcc15d68fdeae777ffe3dd74c02eab407
	https://git.kernel.org/stable/c/0ab4951c1473c7d1ceaf1232eb927109cd1c4859
	https://git.kernel.org/stable/c/dca4e74a918586913d251c0b359e8cc96a3883ea
	https://git.kernel.org/stable/c/889a0d3a35fdedba1c5dcb6410c95c32421680ec
	https://git.kernel.org/stable/c/59458fa4ddb47e7891c61b4a928d13d5f5b00aa0