linux-cve-announce - CVE-2022-49546: x86/kexec: fix memory leak of elf header buffer

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Message-ID: <2025022615-CVE-2022-49546-8673@gregkh>
Date: Wed, 26 Feb 2025 03:13:40 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49546: x86/kexec: fix memory leak of elf header buffer

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

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

x86/kexec: fix memory leak of elf header buffer

This is reported by kmemleak detector:

unreferenced object 0xffffc900002a9000 (size 4096):
  comm "kexec", pid 14950, jiffies 4295110793 (age 373.951s)
  hex dump (first 32 bytes):
    7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00  .ELF............
    04 00 3e 00 01 00 00 00 00 00 00 00 00 00 00 00  ..>.............
  backtrace:
    [<0000000016a8ef9f>] __vmalloc_node_range+0x101/0x170
    [<000000002b66b6c0>] __vmalloc_node+0xb4/0x160
    [<00000000ad40107d>] crash_prepare_elf64_headers+0x8e/0xcd0
    [<0000000019afff23>] crash_load_segments+0x260/0x470
    [<0000000019ebe95c>] bzImage64_load+0x814/0xad0
    [<0000000093e16b05>] arch_kexec_kernel_image_load+0x1be/0x2a0
    [<000000009ef2fc88>] kimage_file_alloc_init+0x2ec/0x5a0
    [<0000000038f5a97a>] __do_sys_kexec_file_load+0x28d/0x530
    [<0000000087c19992>] do_syscall_64+0x3b/0x90
    [<0000000066e063a4>] entry_SYSCALL_64_after_hwframe+0x44/0xae

In crash_prepare_elf64_headers(), a buffer is allocated via vmalloc() to
store elf headers.  While it's not freed back to system correctly when
kdump kernel is reloaded or unloaded.  Then memory leak is caused.  Fix it
by introducing x86 specific function arch_kimage_file_post_load_cleanup(),
and freeing the buffer there.

And also remove the incorrect elf header buffer freeing code.  Before
calling arch specific kexec_file loading function, the image instance has
been initialized.  So 'image->elf_headers' must be NULL.  It doesn't make
sense to free the elf header buffer in the place.

Three different people have reported three bugs about the memory leak on
x86_64 inside Redhat.

The Linux kernel CVE team has assigned CVE-2022-49546 to this issue.


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

	Fixed in 5.15.46 with commit 8765a423a87d74ef24ea02b43b2728fe4039f248
	Fixed in 5.17.14 with commit 115ee42a4c2f26ba2b4ace2668a3f004621f6833
	Fixed in 5.18.3 with commit f675e3a9189d84a9324ab45b0cb19906c2bc8fcb
	Fixed in 5.19 with commit b3e34a47f98974d0844444c5121aaff123004e57

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-2022-49546
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:
	arch/x86/kernel/machine_kexec_64.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/8765a423a87d74ef24ea02b43b2728fe4039f248
	https://git.kernel.org/stable/c/115ee42a4c2f26ba2b4ace2668a3f004621f6833
	https://git.kernel.org/stable/c/f675e3a9189d84a9324ab45b0cb19906c2bc8fcb
	https://git.kernel.org/stable/c/b3e34a47f98974d0844444c5121aaff123004e57