CVE-2026-97942
Received Received - Intake

Kernel BUG in Linux x86 Alternatives Code

Publication date: 2026-09-25

Last updated on: 2026-09-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: x86/alternatives: Exclude text poking against change_page_attr() From time to time, the following BUG can be observed in the x86 alternatives patching code [0]: > kernel BUG at arch/x86/kernel/alternative.c:2576! > Oops: invalid opcode: 0000 [#1] SMP NOPTI > CPU: 0 UID: 0 PID: 355 Comm: (udev-worker) Not tainted 7.1.3-1-default #1 PREEMPT(full) openSUSE Tumbleweed 8c1795b03ec64f997e57a8ad38b1161e3b98da64 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 > RIP: 0010:__text_poke+0x2aa/0x450 > Call Trace: > <TASK> > smp_text_poke_batch_finish+0x2a7/0x320 > __static_call_transform+0xb7/0x220 > arch_static_call_transform+0x5b/0xb0 > __static_call_init+0xe9/0x270 > static_call_module_notify+0x11f/0x150 > notifier_call_chain+0x61/0xe0 > blocking_notifier_call_chain_robust+0x63/0xc0 > load_module+0x1c92/0x20c0 > init_module_from_file+0xd8/0x140 > idempotent_init_module+0x100/0x2f0 > __x64_sys_finit_module+0x71/0xe0 > do_syscall_64+0xe1/0x610 > entry_SYSCALL_64_after_hwframe+0x76/0x7e which matches the following BUG_ON() in alternative.c: /* * If something went wrong, crash and burn since recovery paths are not * implemented. */ BUG_ON(!pages[0] || (cross_page_boundary && !pages[1])); This can happen if vmalloc_to_page() fails, for any reason. Such can happen if text poking races with CPA, which can possibly result in the collapsing of page tables (or breaking of PMD hugepages). It is not a problem for most users of vmalloc_to_page() (they solely own the vmalloc'd range) but, when CONFIG_ARCH_HAS_EXECMEM_ROX=y, various modules own a single execmem vmalloc range, and can call set_memory_*() in parallel on it. This can happen to race against __text_poke and cause havoc in vmalloc_to_page(). Fix it by excluding against CPA using the init_mm mmap read lock. [ dhansen: Fix up SoB ordering. The actual code flow here was: Pedro=>Lorenzo=>Mike=>Me which is reflected in the SoB chain now. I *believe* Mike simply picked up Lorenzo's update to Pedro's post from the Link ]

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Meta Information

Published
2026-09-25
Last Modified
2026-09-25
Generated
2026-09-25
AI Q&A
2026-09-25
EPSS Evaluated
N/A
NVD
CVE-2026-97942
EUVD
EUVD-2026-86796

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 7.1.3-1-default

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a race condition in the x86 alternatives patching code. It occurs when text poking operations conflict with changes to page attributes (CPA), potentially causing a kernel bug or crash. The issue arises when vmalloc_to_page() fails due to concurrent operations, such as collapsing page tables or breaking PMD hugepages.

Impact Analysis

This vulnerability can lead to kernel crashes or instability, particularly on systems using the CONFIG_ARCH_HAS_EXECMEM_ROX=y configuration. It may cause unexpected system freezes or reboots, disrupting normal operations and potentially leading to data loss or service interruptions.

Mitigation Strategies

Apply the Linux kernel patch that resolves the x86/alternatives text poking issue. Update to a kernel version that includes the fix for the BUG_ON() condition in alternative.c. Ensure CONFIG_ARCH_HAS_EXECMEM_ROX=y is properly handled in your kernel configuration.

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