Bug 2535186 (CVE-2026-89926)

Summary: CVE-2026-89926 kernel: KVM: s390: Fix length check __import_wp_info()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's KVM s390 component. A local user can exploit this vulnerability by providing a specially crafted length value to the hardware breakpoint (kvm_hw_breakpoint) mechanism. This integer truncation can lead to an attempted allocation of over 4GB of memory, causing the system to issue a warning and potentially resulting in a denial of service (DoS).
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Description OSIDB Bzimport 2026-09-16 11:16:53 UTC 
In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: Fix length check __import_wp_info()

struct kvm_hw_breakpoint::len is a __u64 that is fully controlled by user
space. This is then assigned to wp_info->len, which is an int. The bounds
check is done on the truncated value while the allocation uses the
untruncated one:

	wp_info->len = bp_data->len;
	[...]
	if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
		return -EINVAL;

	wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL_ACCOUNT);

Use the validated value for the allocation as intended. Without this
fix userspace can trigger >4GB allocations which will fail and result
in a WARN due to MAX_PAGE_ORDER.
Comment 1 Keith Grant 2026-09-16 15:56:39 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89926.mbox