linux-cve-announce - CVE-2024-56613: sched/numa: fix memory leak due to the overwritten vma->numab

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Message-ID: <2024122707-CVE-2024-56613-0897@gregkh>
Date: Fri, 27 Dec 2024 15:51:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-56613: sched/numa: fix memory leak due to the overwritten vma->numab_state

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

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

sched/numa: fix memory leak due to the overwritten vma->numab_state

[Problem Description]
When running the hackbench program of LTP, the following memory leak is
reported by kmemleak.

  # /opt/ltp/testcases/bin/hackbench 20 thread 1000
  Running with 20*40 (== 800) tasks.

  # dmesg | grep kmemleak
  ...
  kmemleak: 480 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
  kmemleak: 665 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

  # cat /sys/kernel/debug/kmemleak
  unreferenced object 0xffff888cd8ca2c40 (size 64):
    comm "hackbench", pid 17142, jiffies 4299780315
    hex dump (first 32 bytes):
      ac 74 49 00 01 00 00 00 4c 84 49 00 01 00 00 00  .tI.....L.I.....
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    backtrace (crc bff18fd4):
      [<ffffffff81419a89>] __kmalloc_cache_noprof+0x2f9/0x3f0
      [<ffffffff8113f715>] task_numa_work+0x725/0xa00
      [<ffffffff8110f878>] task_work_run+0x58/0x90
      [<ffffffff81ddd9f8>] syscall_exit_to_user_mode+0x1c8/0x1e0
      [<ffffffff81dd78d5>] do_syscall_64+0x85/0x150
      [<ffffffff81e0012b>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
  ...

This issue can be consistently reproduced on three different servers:
  * a 448-core server
  * a 256-core server
  * a 192-core server

[Root Cause]
Since multiple threads are created by the hackbench program (along with
the command argument 'thread'), a shared vma might be accessed by two or
more cores simultaneously. When two or more cores observe that
vma->numab_state is NULL at the same time, vma->numab_state will be
overwritten.

Although current code ensures that only one thread scans the VMAs in a
single 'numa_scan_period', there might be a chance for another thread
to enter in the next 'numa_scan_period' while we have not gotten till
numab_state allocation [1].

Note that the command `/opt/ltp/testcases/bin/hackbench 50 process 1000`
cannot the reproduce the issue. It is verified with 200+ test runs.

[Solution]
Use the cmpxchg atomic operation to ensure that only one thread executes
the vma->numab_state assignment.

[1] https://lore.kernel.org/lkml/1794be3c-358c-4cdc-a43d-a1f841d91ef7@amd.com/

The Linux kernel CVE team has assigned CVE-2024-56613 to this issue.

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

	Issue introduced in 6.4 with commit ef6a22b70f6d90449a5c797b8968a682824e2011 and fixed in 6.6.66 with commit 8f149bcc4d91ac92b32ff4949b291e6ed883dc42
	Issue introduced in 6.4 with commit ef6a22b70f6d90449a5c797b8968a682824e2011 and fixed in 6.12.5 with commit a71ddd5b87cda687efa28e049e85e923689bcef9
	Issue introduced in 6.4 with commit ef6a22b70f6d90449a5c797b8968a682824e2011 and fixed in 6.13-rc2 with commit 5f1b64e9a9b7ee9cfd32c6b2fab796e29bfed075

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-2024-56613
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/sched/fair.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/8f149bcc4d91ac92b32ff4949b291e6ed883dc42
	https://git.kernel.org/stable/c/a71ddd5b87cda687efa28e049e85e923689bcef9
	https://git.kernel.org/stable/c/5f1b64e9a9b7ee9cfd32c6b2fab796e29bfed075