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CVE-2023-52849

Disclosure Date: May 21, 2024 •
CVE-2023-52849
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Description

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

cxl/mem: Fix shutdown order

Ira reports that removing cxl_mock_mem causes a crash with the following
trace:

BUG: kernel NULL pointer dereference, address: 0000000000000044
[..]
RIP: 0010:cxl_region_decode_reset+0x7f/0x180 [cxl_core]
[..]
Call Trace:
<TASK>
cxl_region_detach+0xe8/0x210 [cxl_core]
cxl_decoder_kill_region+0x27/0x40 [cxl_core]
cxld_unregister+0x29/0x40 [cxl_core]
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1d2/0x210
bus_remove_device+0xd7/0x150
device_del+0x155/0x3e0
device_unregister+0x13/0x60
devm_release_action+0x4d/0x90
? __pfx_unregister_port+0x10/0x10 [cxl_core]
delete_endpoint+0x121/0x130 [cxl_core]
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1d2/0x210
bus_remove_device+0xd7/0x150
device_del+0x155/0x3e0
? lock_release+0x142/0x290
cdev_device_del+0x15/0x50
cxl_memdev_unregister+0x54/0x70 [cxl_core]

This crash is due to the clearing out the cxl_memdev’s driver context
(@cxlds) before the subsystem is done with it. This is ultimately due to
the region(s), that this memdev is a member, being torn down and expecting
to be able to de-reference @cxlds, like here:

static int cxl_region_decode_reset(struct cxl_region *cxlr, int count)
…

            if (cxlds->rcd)
                    goto endpoint_reset;

…

Fix it by keeping the driver context valid until memdev-device
unregistration, and subsequently the entire stack of related
dependencies, unwinds.

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CVSS V3 Severity and Metrics
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Impact Score:
Unknown
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Attack Vector (AV):
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Integrity (I):
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General Information

Offensive Application
Unknown
Utility Class
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Ports
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OS
Unknown
Vulnerable Versions
Linux 20bd0198bebd
Linux not down converted
Prerequisites
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Discovered By
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PoC Author
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Metasploit Module
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Reporter
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Vendors

  • Linux

Products

  • Linux
Technical Analysis