linux-cve-announce - CVE-2024-49980: vrf: revert "vrf: Remove unnecessary RCU-bh critical section"

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Message-ID: <2024102135-CVE-2024-49980-da73@gregkh>
Date: Mon, 21 Oct 2024 20:03:08 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-49980: vrf: revert "vrf: Remove unnecessary RCU-bh critical section"

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

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

vrf: revert "vrf: Remove unnecessary RCU-bh critical section"

This reverts commit 504fc6f4f7f681d2a03aa5f68aad549d90eab853.

dev_queue_xmit_nit is expected to be called with BH disabled.
__dev_queue_xmit has the following:

        /* Disable soft irqs for various locks below. Also
         * stops preemption for RCU.
         */
        rcu_read_lock_bh();

VRF must follow this invariant. The referenced commit removed this
protection. Which triggered a lockdep warning:

	================================
	WARNING: inconsistent lock state
	6.11.0 #1 Tainted: G        W
	--------------------------------
	inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
	btserver/134819 [HC0[0]:SC0[0]:HE1:SE1] takes:
	ffff8882da30c118 (rlock-AF_PACKET){+.?.}-{2:2}, at: tpacket_rcv+0x863/0x3b30
	{IN-SOFTIRQ-W} state was registered at:
	  lock_acquire+0x19a/0x4f0
	  _raw_spin_lock+0x27/0x40
	  packet_rcv+0xa33/0x1320
	  __netif_receive_skb_core.constprop.0+0xcb0/0x3a90
	  __netif_receive_skb_list_core+0x2c9/0x890
	  netif_receive_skb_list_internal+0x610/0xcc0
          [...]

	other info that might help us debug this:
	 Possible unsafe locking scenario:

	       CPU0
	       ----
	  lock(rlock-AF_PACKET);
	  <Interrupt>
	    lock(rlock-AF_PACKET);

	 *** DEADLOCK ***

	Call Trace:
	 <TASK>
	 dump_stack_lvl+0x73/0xa0
	 mark_lock+0x102e/0x16b0
	 __lock_acquire+0x9ae/0x6170
	 lock_acquire+0x19a/0x4f0
	 _raw_spin_lock+0x27/0x40
	 tpacket_rcv+0x863/0x3b30
	 dev_queue_xmit_nit+0x709/0xa40
	 vrf_finish_direct+0x26e/0x340 [vrf]
	 vrf_l3_out+0x5f4/0xe80 [vrf]
	 __ip_local_out+0x51e/0x7a0
          [...]

The Linux kernel CVE team has assigned CVE-2024-49980 to this issue.


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

	Issue introduced in 6.6 with commit 504fc6f4f7f6 and fixed in 6.6.55 with commit 718a752bd746
	Issue introduced in 6.6 with commit 504fc6f4f7f6 and fixed in 6.10.14 with commit 8c9381b31382
	Issue introduced in 6.6 with commit 504fc6f4f7f6 and fixed in 6.11.3 with commit e61f8c4d179b
	Issue introduced in 6.6 with commit 504fc6f4f7f6 and fixed in 6.12-rc2 with commit b04c4d9eb4f2

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-2024-49980
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:
	drivers/net/vrf.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/718a752bd746b3f4dd62516bb437baf73d548415
	https://git.kernel.org/stable/c/8c9381b3138246d46536db93ed696832abd70204
	https://git.kernel.org/stable/c/e61f8c4d179b2ffc0d3b7f821c3734be738643d0
	https://git.kernel.org/stable/c/b04c4d9eb4f25b950b33218e33b04c94e7445e51