high CVSS 7.8

CVE-2022-49196·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: powerpc/pseries: Fix use after free in remove_phb_dynamic() In remove_phb_dynamic() we use &phb->io_resource, after we've called device_unregister(&host_bridge->dev). But the unregister may have freed phb, because pcibios_free_controller_deferred() is the release function for the host_bridge. If there are no outstanding references when we call device_unregister() then phb will be freed out from under us. This has gone mainly unnoticed, but with slub_debug and page_poison enabled it can lead to a crash: PID: 7574 TASK: c0000000d492cb80 CPU: 13 COMMAND: "drmgr" #0 [c0000000e4f075a0] crash_kexec at c00000000027d7dc #1 [c0000000e4f075d0] oops_end at c000000000029608 #2 [c0000000e4f07650] __bad_page_fault at c0000000000904b4 #3 [c0000000e4f076c0] do_bad_slb_fault at c00000000009a5a8 #4 [c0000000e4f076f0] data_access_slb_common_virt at c000000000008b30 Data SLB Access [380] exception frame: R0: c000000000167250 R1: c0000000e4f07a00 R2: c000000002a46100 R3: c000000002b39ce8 R4: 00000000000000c0 R5: 00000000000000a9 R6: 3894674d000000c0 R7: 0000000000000000 R8: 00000000000000ff R9: 0000000000000100 R10: 6b6b6b6b6b6b6b6b R11: 0000000000008000 R12: c00000000023da80 R13: c0000009ffd38b00 R14: 0000000000000000 R15: 000000011c87f0f0 R16: 0000000000000006 R17: 0000000000000003 R18: 0000000000000002 R19: 0000000000000004 R20: 0000000000000005 R21: 000000011c87ede8 R22: 000000011c87c5a8 R23: 000000011c87d3a0 R24: 0000000000000000 R25: 0000000000000001 R26: c0000000e4f07cc8 R27: c00000004d1cc400 R28: c0080000031d00e8 R29: c00000004d23d800 R30: c00000004d1d2400 R31: c00000004d1d2540 NIP: c000000000167258 MSR: 8000000000009033 OR3: c000000000e9f474 CTR: 0000000000000000 LR: c000000000167250 XER: 0000000020040003 CCR: 0000000024088420 MQ: 0000000000000000 DAR: 6b6b6b6b6b6b6ba3 DSISR: c0000000e4f07920 Syscall Result: fffffffffffffff2 [NIP : release_resource+56] [LR : release_resource+48] #5 [c0000000e4f07a00] release_resource at c000000000167258 (unreliable) #6 [c0000000e4f07a30] remove_phb_dynamic at c000000000105648 #7 [c0000000e4f07ab0] dlpar_remove_slot at c0080000031a09e8 [rpadlpar_io] #8 [c0000000e4f07b50] remove_slot_store at c0080000031a0b9c [rpadlpar_io] #9 [c0000000e4f07be0] kobj_attr_store at c000000000817d8c #10 [c0000000e4f07c00] sysfs_kf_write at c00000000063e504 #11 [c0000000e4f07c20] kernfs_fop_write_iter at c00000000063d868 #12 [c0000000e4f07c70] new_sync_write at c00000000054339c #13 [c0000000e4f07d10] vfs_write at c000000000546624 #14 [c0000000e4f07d60] ksys_write at c0000000005469f4 #15 [c0000000e4f07db0] system_call_exception at c000000000030840 #16 [c0000000e4f07e10] system_call_vectored_common at c00000000000c168 To avoid it, we can take a reference to the host_bridge->dev until we're done using phb. Then when we drop the reference the phb will be freed.

Severity: high
Software: Kernel
Fixed in: 5.17.2
Published: 2025-02-26

Affected versions

From: 5.17

Until: 5.17.2

Fixed in: 5.17.2

How to fix this CVE

Update your Linux kernel to version 5.17.2 or later to resolve a critical use-after-free vulnerability in PowerPC PCI host bridge removal. This flaw can cause kernel crashes during dynamic PCI slot removal operations on POWER systems. Apply the patch immediately to prevent unexpected system failures.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

Check the current kernel version: uname -r
Verify if your system is PowerPC-based: uname -m (look for ppc64, ppc64le)
Review system logs for crashes during PCI device hotplug operations: dmesg | grep -i 'phb\|pci.*hot'
Confirm the patch is applied by checking kernel source commit hash: grep -i 'remove_phb_dynamic' /boot/config-$(uname -r) || strings /boot/vmlinuz-$(uname -r) | grep -i phb_dynamic
Verify the installed kernel is >= 5.17.2: if [[ $(uname -r | cut -d. -f1-3) < 5.17.2 ]]; then echo 'Vulnerable'; fi

FAQ

What is CVE-2022-49196?

CVE-2022-49196 is a use-after-free vulnerability in the Linux kernel's PowerPC PCI subsystem where the remove_phb_dynamic() function references freed memory after calling device_unregister(). This occurs because the host bridge device release function may deallocate the PCI host bridge structure prematurely, causing crashes when memory debugging is enabled.

Is CVE-2022-49196 being actively exploited?

No, CVE-2022-49196 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it causes crashes on affected systems, particularly when slub_debug and page_poison are enabled.

What versions of Kernel are affected by CVE-2022-49196?

Linux kernel versions 5.17 through 5.17.1 are affected. The vulnerability was fixed in kernel version 5.17.2 and later. This issue only impacts PowerPC-based systems running these kernel versions.

How do I check if my server is vulnerable to CVE-2022-49196?

Run 'uname -r' to check your kernel version—if it shows 5.17.0, 5.17.1, or 5.17 with a minor version less than 2, you are vulnerable. Additionally, verify you are on PowerPC architecture with 'uname -m' (should show ppc64 or ppc64le). Vulnerable systems will crash when performing PCI slot removal operations.

Does Defensia detect CVE-2022-49196?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored PowerPC server, CVE-2022-49196 will appear in your dashboard with remediation steps.

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References

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