Updated: 2026-03-05 00:27:38.091183
Description:
In the Linux kernel, the following vulnerability has been resolved: x86/alternatives: Disable KASAN in apply_alternatives() Fei has reported that KASAN triggers during apply_alternatives() on a 5-level paging machine: BUG: KASAN: out-of-bounds in rcu_is_watching() Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0 ... __asan_load4() rcu_is_watching() trace_hardirqs_on() text_poke_early() apply_alternatives() ... On machines with 5-level paging, cpu_feature_enabled(X86_FEATURE_LA57) gets patched. It includes KASAN code, where KASAN_SHADOW_START depends on __VIRTUAL_MASK_SHIFT, which is defined with cpu_feature_enabled(). KASAN gets confused when apply_alternatives() patches the KASAN_SHADOW_START users. A test patch that makes KASAN_SHADOW_START static, by replacing __VIRTUAL_MASK_SHIFT with 56, works around the issue. Fix it for real by disabling KASAN while the kernel is patching alternatives. [ mingo: updated the changelog ]
| Links | NIST | CIRCL | RHEL | Ubuntu |
| Severity | Score | |
|---|---|---|
| CVSS Version 2.x | 0.0 | |
| CVSS Version 3.x | HIGH | 7.1 |
| OS name | Project name | Version | Score | Severity | Status | Errata | Last updated | Statement |
|---|---|---|---|---|---|---|---|---|
| AlmaLinux 9.2 ESU | kernel | 5.14.0 | 7.1 | HIGH | Released | CLSA-2025:1743193221 | 2025-02-05 02:21:29 | |
| CentOS 8.4 ELS | kernel | 4.18.0 | 7.1 | HIGH | Released | CLSA-2025:1736778412 | 2025-11-27 20:38:40 | |
| CentOS 8.5 ELS | kernel | 4.18.0 | 7.1 | HIGH | Released | CLSA-2025:1736778632 | 2025-11-27 20:38:40 | |
| Ubuntu 16.04 ELS | linux | 4.4.0 | 7.1 | HIGH | Not Vulnerable | 2024-06-13 11:19:53 | Not affected: the faulty code path exists only on x86 kernels that patch cpu_feature_enabled(X86_FEA... | |
| Ubuntu 18.04 ELS | linux | 4.15.0 | 7.1 | HIGH | Not Vulnerable | 2024-06-13 11:19:53 | Not affected: This issue was introduced upstream in Linux v4.17-rc1 by commit 6657fca06e3f, so kerne... |