linux-cve-announce - CVE-2024-50222: iov_iter: fix copy_page_from_iter_atomic() if KMAP_LOCAL_FORCE

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Message-ID: <2024110926-CVE-2024-50222-4e8c@gregkh>
Date: Sat,  9 Nov 2024 11:15:30 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50222: iov_iter: fix copy_page_from_iter_atomic() if KMAP_LOCAL_FORCE_MAP

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

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

iov_iter: fix copy_page_from_iter_atomic() if KMAP_LOCAL_FORCE_MAP

generic/077 on x86_32 CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y with highmem,
on huge=always tmpfs, issues a warning and then hangs (interruptibly):

WARNING: CPU: 5 PID: 3517 at mm/highmem.c:622 kunmap_local_indexed+0x62/0xc9
CPU: 5 UID: 0 PID: 3517 Comm: cp Not tainted 6.12.0-rc4 #2
...
copy_page_from_iter_atomic+0xa6/0x5ec
generic_perform_write+0xf6/0x1b4
shmem_file_write_iter+0x54/0x67

Fix copy_page_from_iter_atomic() by limiting it in that case
(include/linux/skbuff.h skb_frag_must_loop() does similar).

But going forward, perhaps CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is too
surprising, has outlived its usefulness, and should just be removed?

The Linux kernel CVE team has assigned CVE-2024-50222 to this issue.


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

	Issue introduced in 6.6 with commit 908a1ad89466 and fixed in 6.6.60 with commit 4f7ffa83fa79
	Issue introduced in 6.6 with commit 908a1ad89466 and fixed in 6.11.7 with commit 3a303409f271
	Issue introduced in 6.6 with commit 908a1ad89466 and fixed in 6.12-rc6 with commit c749d9b7ebbc

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-2024-50222
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:
	lib/iov_iter.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/4f7ffa83fa79dd52efbaef366c850aaaae06a469
	https://git.kernel.org/stable/c/3a303409f271dfe0987b8f79595138340497a32d
	https://git.kernel.org/stable/c/c749d9b7ebbc5716af7a95f7768634b30d9446ec