CVE-2024-50226

CVE Details

Release Date:

2024-11-09

Description

In the Linux kernel, the following vulnerability has been resolved:\ncxl/port: Fix use-after-free, permit out-of-order decoder shutdown\nIn support of investigating an initialization failure report [1],\ncxl_test was updated to register mock memory-devices after the mock\nroot-port/bus device had been registered. That led to cxl_test crashing\nwith a use-after-free bug with the following signature:\ncxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem0:decoder7.0 @ 0 next: cxl_switch_uport.0 nr_eps: 1 nr_targets: 1\ncxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem4:decoder14.0 @ 1 next: cxl_switch_uport.0 nr_eps: 2 nr_targets: 1\ncxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[0] = cxl_switch_dport.0 for mem0:decoder7.0 @ 0\n1) cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[1] = cxl_switch_dport.4 for mem4:decoder14.0 @ 1\n[..]\ncxld_unregister: cxl decoder14.0:\ncxl_region_decode_reset: cxl_region region3:\nmock_decoder_reset: cxl_port port3: decoder3.0 reset\n2) mock_decoder_reset: cxl_port port3: decoder3.0: out of order reset, expected decoder3.1\ncxl_endpoint_decoder_release: cxl decoder14.0:\n[..]\ncxld_unregister: cxl decoder7.0:\n3) cxl_region_decode_reset: cxl_region region3:\nOops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bc3: 0000 [#1] PREEMPT SMP PTI\n[..]\nRIP: 0010:to_cxl_port+0x8/0x60 [cxl_core]\n[..]\nCall Trace:\n\ncxl_region_decode_reset+0x69/0x190 [cxl_core]\ncxl_region_detach+0xe8/0x210 [cxl_core]\ncxl_decoder_kill_region+0x27/0x40 [cxl_core]\ncxld_unregister+0x5d/0x60 [cxl_core]\nAt 1) a region has been established with 2 endpoint decoders (7.0 and\n14.0). Those endpoints share a common switch-decoder in the topology\n(3.0). At teardown, 2), decoder14.0 is the first to be removed and hits\nthe 'out of order reset case' in the switch decoder. The effect though\nis that region3 cleanup is aborted leaving it in-tact and\nreferencing decoder14.0. At 3) the second attempt to teardown region3\ntrips over the stale decoder14.0 object which has long since been\ndeleted.\nThe fix here is to recognize that the CXL specification places no\nmandate on in-order shutdown of switch-decoders, the driver enforces\nin-order allocation, and hardware enforces in-order commit. So, rather\nthan fail and leave objects dangling, always remove them.\nIn support of making cxl_region_decode_reset() always succeed,\ncxl_region_invalidate_memregion() failures are turned into warnings.\nCrashing the kernel is ok there since system integrity is at risk if\ncaches cannot be managed around physical address mutation events like\nCXL region destruction.\nA new device_for_each_child_reverse_from() is added to cleanup\nport->commit_end after all dependent decoders have been disabled. In\nother words if decoders are allocated 0->1->2 and disabled 1->2->0 then\nport->commit_end only decrements from 2 after 2 has been disabled, and\nit decrements all the way to zero since 1 was disabled previously.

See more information about CVE-2024-50226 from MITRE CVE dictionary and NIST NVD

NOTE: The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 metrics

Base Score:	5.5
Vector String:	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Version:	3.1
Attack Vector:	Local
Attack Complexity:	Low
Privileges Required:	Low
User Interaction:	None
Scope:	Unchanged
Confidentiality:	None
Integrity:	None
Availability:	High

Errata information

Platform	Errata	Release Date
Oracle Linux version 9 (kernel)	ELSA-2024-10274	2024-11-26