cve/published/2024/CVE-2024-43887.mbox - pub/scm/linux/security/vulns - Git at Google

 From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
 From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 To: <linux-cve-announce@vger.kernel.org>
 Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
 Subject: CVE-2024-43887: net/tcp: Disable TCP-AO static key after RCU grace period

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

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

 net/tcp: Disable TCP-AO static key after RCU grace period

 The lifetime of TCP-AO static_key is the same as the last
 tcp_ao_info. On the socket destruction tcp_ao_info ceases to be
 with RCU grace period, while tcp-ao static branch is currently deferred
 destructed. The static key definition is
 : DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ);

 which means that if RCU grace period is delayed by more than a second
 and tcp_ao_needed is in the process of disablement, other CPUs may
 yet see tcp_ao_info which atent dead, but soon-to-be.
 And that breaks the assumption of static_key_fast_inc_not_disabled().

 See the comment near the definition:
 > * The caller must make sure that the static key can't get disabled while
 > * in this function. It doesn't patch jump labels, only adds a user to
 > * an already enabled static key.

 Originally it was introduced in commit eb8c507296f6 ("jump_label:
 Prevent key->enabled int overflow"), which is needed for the atomic
 contexts, one of which would be the creation of a full socket from a
 request socket. In that atomic context, it's known by the presence
 of the key (md5/ao) that the static branch is already enabled.
 So, the ref counter for that static branch is just incremented
 instead of holding the proper mutex.
 static_key_fast_inc_not_disabled() is just a helper for such usage
 case. But it must not be used if the static branch could get disabled
 in parallel as it's not protected by jump_label_mutex and as a result,
 races with jump_label_update() implementation details.

 Happened on netdev test-bot[1], so not a theoretical issue:

 [] jump_label: Fatal kernel bug, unexpected op at tcp_inbound_hash+0x1a7/0x870 [ffffffffa8c4e9b7] (eb 50 0f 1f 44 != 66 90 0f 1f 00)) size:2 type:1
 [] ------------[ cut here ]------------
 [] kernel BUG at arch/x86/kernel/jump_label.c:73!
 [] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
 [] CPU: 3 PID: 243 Comm: kworker/3:3 Not tainted 6.10.0-virtme #1
 [] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
 [] Workqueue: events jump_label_update_timeout
 [] RIP: 0010:__jump_label_patch+0x2f6/0x350
 ...
 [] Call Trace:
 []  <TASK>
 []  arch_jump_label_transform_queue+0x6c/0x110
 []  __jump_label_update+0xef/0x350
 []  __static_key_slow_dec_cpuslocked.part.0+0x3c/0x60
 []  jump_label_update_timeout+0x2c/0x40
 []  process_one_work+0xe3b/0x1670
 []  worker_thread+0x587/0xce0
 []  kthread+0x28a/0x350
 []  ret_from_fork+0x31/0x70
 []  ret_from_fork_asm+0x1a/0x30
 []  </TASK>
 [] Modules linked in: veth
 [] ---[ end trace 0000000000000000 ]---
 [] RIP: 0010:__jump_label_patch+0x2f6/0x350

 [1]: https://netdev-3.bots.linux.dev/vmksft-tcp-ao-dbg/results/696681/5-connect-deny-ipv6/stderr

 The Linux kernel CVE team has assigned CVE-2024-43887 to this issue.


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

 	Issue introduced in 6.7 with commit 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 and fixed in 6.10.5 with commit 954d55a59b2501f4a9bd693b40ce45a1c46cb2b3
 	Issue introduced in 6.7 with commit 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 and fixed in 6.11 with commit 14ab4792ee120c022f276a7e4768f4dcb08f0cdd

 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-2024-43887
 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:
 	net/ipv4/tcp_ao.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/954d55a59b2501f4a9bd693b40ce45a1c46cb2b3
 	https://git.kernel.org/stable/c/14ab4792ee120c022f276a7e4768f4dcb08f0cdd
	From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
	From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
	To: <linux-cve-announce@vger.kernel.org>
	Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
	Subject: CVE-2024-43887: net/tcp: Disable TCP-AO static key after RCU grace period

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

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

	net/tcp: Disable TCP-AO static key after RCU grace period

	The lifetime of TCP-AO static_key is the same as the last
	tcp_ao_info. On the socket destruction tcp_ao_info ceases to be
	with RCU grace period, while tcp-ao static branch is currently deferred
	destructed. The static key definition is
	: DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ);

	which means that if RCU grace period is delayed by more than a second
	and tcp_ao_needed is in the process of disablement, other CPUs may
	yet see tcp_ao_info which atent dead, but soon-to-be.
	And that breaks the assumption of static_key_fast_inc_not_disabled().

	See the comment near the definition:
	> * The caller must make sure that the static key can't get disabled while
	> * in this function. It doesn't patch jump labels, only adds a user to
	> * an already enabled static key.

	Originally it was introduced in commit eb8c507296f6 ("jump_label:
	Prevent key->enabled int overflow"), which is needed for the atomic
	contexts, one of which would be the creation of a full socket from a
	request socket. In that atomic context, it's known by the presence
	of the key (md5/ao) that the static branch is already enabled.
	So, the ref counter for that static branch is just incremented
	instead of holding the proper mutex.
	static_key_fast_inc_not_disabled() is just a helper for such usage
	case. But it must not be used if the static branch could get disabled
	in parallel as it's not protected by jump_label_mutex and as a result,
	races with jump_label_update() implementation details.

	Happened on netdev test-bot[1], so not a theoretical issue:

	[] jump_label: Fatal kernel bug, unexpected op at tcp_inbound_hash+0x1a7/0x870 [ffffffffa8c4e9b7] (eb 50 0f 1f 44 != 66 90 0f 1f 00)) size:2 type:1
	[] ------------[ cut here ]------------
	[] kernel BUG at arch/x86/kernel/jump_label.c:73!
	[] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
	[] CPU: 3 PID: 243 Comm: kworker/3:3 Not tainted 6.10.0-virtme #1
	[] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
	[] Workqueue: events jump_label_update_timeout
	[] RIP: 0010:__jump_label_patch+0x2f6/0x350
	...
	[] Call Trace:
	[] <TASK>
	[] arch_jump_label_transform_queue+0x6c/0x110
	[] __jump_label_update+0xef/0x350
	[] __static_key_slow_dec_cpuslocked.part.0+0x3c/0x60
	[] jump_label_update_timeout+0x2c/0x40
	[] process_one_work+0xe3b/0x1670
	[] worker_thread+0x587/0xce0
	[] kthread+0x28a/0x350
	[] ret_from_fork+0x31/0x70
	[] ret_from_fork_asm+0x1a/0x30
	[] </TASK>
	[] Modules linked in: veth
	[] ---[ end trace 0000000000000000 ]---
	[] RIP: 0010:__jump_label_patch+0x2f6/0x350

	[1]: https://netdev-3.bots.linux.dev/vmksft-tcp-ao-dbg/results/696681/5-connect-deny-ipv6/stderr

	The Linux kernel CVE team has assigned CVE-2024-43887 to this issue.


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

	Issue introduced in 6.7 with commit 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 and fixed in 6.10.5 with commit 954d55a59b2501f4a9bd693b40ce45a1c46cb2b3
	Issue introduced in 6.7 with commit 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 and fixed in 6.11 with commit 14ab4792ee120c022f276a7e4768f4dcb08f0cdd

	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-2024-43887
	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:
	net/ipv4/tcp_ao.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/954d55a59b2501f4a9bd693b40ce45a1c46cb2b3
	https://git.kernel.org/stable/c/14ab4792ee120c022f276a7e4768f4dcb08f0cdd