linux-cve-announce - CVE-2024-50219: mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves

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Message-ID: <2024110925-CVE-2024-50219-c970@gregkh>
Date: Sat,  9 Nov 2024 11:15:27 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50219: mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves

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

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

mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves

Under memory pressure it's possible for GFP_ATOMIC order-0 allocations to
fail even though free pages are available in the highatomic reserves. 
GFP_ATOMIC allocations cannot trigger unreserve_highatomic_pageblock()
since it's only run from reclaim.

Given that such allocations will pass the watermarks in
__zone_watermark_unusable_free(), it makes sense to fallback to highatomic
reserves the same way that ALLOC_OOM can.

This fixes order-0 page allocation failures observed on Cloudflare's fleet
when handling network packets:

  kswapd1: page allocation failure: order:0, mode:0x820(GFP_ATOMIC),
  nodemask=(null),cpuset=/,mems_allowed=0-7
  CPU: 10 PID: 696 Comm: kswapd1 Kdump: loaded Tainted: G           O 6.6.43-CUSTOM #1
  Hardware name: MACHINE
  Call Trace:
   <IRQ>
   dump_stack_lvl+0x3c/0x50
   warn_alloc+0x13a/0x1c0
   __alloc_pages_slowpath.constprop.0+0xc9d/0xd10
   __alloc_pages+0x327/0x340
   __napi_alloc_skb+0x16d/0x1f0
   bnxt_rx_page_skb+0x96/0x1b0 [bnxt_en]
   bnxt_rx_pkt+0x201/0x15e0 [bnxt_en]
   __bnxt_poll_work+0x156/0x2b0 [bnxt_en]
   bnxt_poll+0xd9/0x1c0 [bnxt_en]
   __napi_poll+0x2b/0x1b0
   bpf_trampoline_6442524138+0x7d/0x1000
   __napi_poll+0x5/0x1b0
   net_rx_action+0x342/0x740
   handle_softirqs+0xcf/0x2b0
   irq_exit_rcu+0x6c/0x90
   sysvec_apic_timer_interrupt+0x72/0x90
   </IRQ>

[mfleming@...udflare.com: update comment]
  Link: https://lkml.kernel.org/r/20241015125158.3597702-1-matt@readmodwrite.com

The Linux kernel CVE team has assigned CVE-2024-50219 to this issue.


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

	Issue introduced in 5.9 with commit 1d91df85f399 and fixed in 5.15.171 with commit 4c4e238d3ada
	Issue introduced in 5.9 with commit 1d91df85f399 and fixed in 6.1.116 with commit 189b954469cf
	Issue introduced in 5.9 with commit 1d91df85f399 and fixed in 6.6.60 with commit b958948ae1cb
	Issue introduced in 5.9 with commit 1d91df85f399 and fixed in 6.11.7 with commit d0fdacfb85a3
	Issue introduced in 5.9 with commit 1d91df85f399 and fixed in 6.12-rc6 with commit 281dd25c1a01

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-2024-50219
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:
	mm/page_alloc.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/4c4e238d3adad3c94bb255d0f117d3685bbfdd33
	https://git.kernel.org/stable/c/189b954469cf82f8b8cf496f8de94b006d2d4746
	https://git.kernel.org/stable/c/b958948ae1cb3e39c48e9f805436fd652103c71e
	https://git.kernel.org/stable/c/d0fdacfb85a3e1223b894cc6e60091ec91049e9e
	https://git.kernel.org/stable/c/281dd25c1a018261a04d1b8bf41a0674000bfe38