| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-46864: x86/hyperv: fix kexec crash due to VP assist page corruption |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/hyperv: fix kexec crash due to VP assist page corruption |
| |
| commit 9636be85cc5b ("x86/hyperv: Fix hyperv_pcpu_input_arg handling when |
| CPUs go online/offline") introduces a new cpuhp state for hyperv |
| initialization. |
| |
| cpuhp_setup_state() returns the state number if state is |
| CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN and 0 for all other states. |
| For the hyperv case, since a new cpuhp state was introduced it would |
| return 0. However, in hv_machine_shutdown(), the cpuhp_remove_state() call |
| is conditioned upon "hyperv_init_cpuhp > 0". This will never be true and |
| so hv_cpu_die() won't be called on all CPUs. This means the VP assist page |
| won't be reset. When the kexec kernel tries to setup the VP assist page |
| again, the hypervisor corrupts the memory region of the old VP assist page |
| causing a panic in case the kexec kernel is using that memory elsewhere. |
| This was originally fixed in commit dfe94d4086e4 ("x86/hyperv: Fix kexec |
| panic/hang issues"). |
| |
| Get rid of hyperv_init_cpuhp entirely since we are no longer using a |
| dynamic cpuhp state and use CPUHP_AP_HYPERV_ONLINE directly with |
| cpuhp_remove_state(). |
| |
| The Linux kernel CVE team has assigned CVE-2024-46864 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.4 with commit 9636be85cc5bdd8b7a7f6a53405cbcc52161c93c and fixed in 6.6.52 with commit 2ae1beb3ab4f28868cc5d1541d05e1fbee3ad825 |
| Issue introduced in 6.4 with commit 9636be85cc5bdd8b7a7f6a53405cbcc52161c93c and fixed in 6.10.11 with commit d6f018a3b49d0a94ddbd0e479c2af6b19724e434 |
| Issue introduced in 6.4 with commit 9636be85cc5bdd8b7a7f6a53405cbcc52161c93c and fixed in 6.11 with commit b9af6418279c4cf73ca073f8ea024992b38be8ab |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-46864 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/x86/hyperv/hv_init.c |
| arch/x86/include/asm/mshyperv.h |
| arch/x86/kernel/cpu/mshyperv.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/2ae1beb3ab4f28868cc5d1541d05e1fbee3ad825 |
| https://git.kernel.org/stable/c/d6f018a3b49d0a94ddbd0e479c2af6b19724e434 |
| https://git.kernel.org/stable/c/b9af6418279c4cf73ca073f8ea024992b38be8ab |
