| From bippy-7c5fe7eed585 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-2025-21991: x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes |
| |
| Currently, load_microcode_amd() iterates over all NUMA nodes, retrieves their |
| CPU masks and unconditionally accesses per-CPU data for the first CPU of each |
| mask. |
| |
| According to Documentation/admin-guide/mm/numaperf.rst: |
| |
| "Some memory may share the same node as a CPU, and others are provided as |
| memory only nodes." |
| |
| Therefore, some node CPU masks may be empty and wouldn't have a "first CPU". |
| |
| On a machine with far memory (and therefore CPU-less NUMA nodes): |
| - cpumask_of_node(nid) is 0 |
| - cpumask_first(0) is CONFIG_NR_CPUS |
| - cpu_data(CONFIG_NR_CPUS) accesses the cpu_info per-CPU array at an |
| index that is 1 out of bounds |
| |
| This does not have any security implications since flashing microcode is |
| a privileged operation but I believe this has reliability implications by |
| potentially corrupting memory while flashing a microcode update. |
| |
| When booting with CONFIG_UBSAN_BOUNDS=y on an AMD machine that flashes |
| a microcode update. I get the following splat: |
| |
| UBSAN: array-index-out-of-bounds in arch/x86/kernel/cpu/microcode/amd.c:X:Y |
| index 512 is out of range for type 'unsigned long[512]' |
| [...] |
| Call Trace: |
| dump_stack |
| __ubsan_handle_out_of_bounds |
| load_microcode_amd |
| request_microcode_amd |
| reload_store |
| kernfs_fop_write_iter |
| vfs_write |
| ksys_write |
| do_syscall_64 |
| entry_SYSCALL_64_after_hwframe |
| |
| Change the loop to go over only NUMA nodes which have CPUs before determining |
| whether the first CPU on the respective node needs microcode update. |
| |
| [ bp: Massage commit message, fix typo. ] |
| |
| The Linux kernel CVE team has assigned CVE-2025-21991 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.4.235 with commit 979e197968a1e8f09bf0d706801dba4432f85ab3 and fixed in 5.4.292 with commit d509c4731090ebd9bbdb72c70a2d70003ae81f4f |
| Issue introduced in 5.10.173 with commit 44a44b57e88f311c1415be1f567c50050913c149 and fixed in 5.10.236 with commit 985a536e04bbfffb1770df43c6470f635a6b1073 |
| Issue introduced in 5.15.99 with commit be2710deaed3ab1402379a2ede30a3754fe6767a and fixed in 5.15.180 with commit 18b5d857c6496b78ead2fd10001b81ae32d30cac |
| Issue introduced in 6.1.16 with commit d576547f489c935b9897d4acf8beee3325dea8a5 and fixed in 6.1.132 with commit ec52240622c4d218d0240079b7c1d3ec2328a9f4 |
| Issue introduced in 6.3 with commit 7ff6edf4fef38ab404ee7861f257e28eaaeed35f and fixed in 6.6.84 with commit e686349cc19e800dac8971929089ba5ff59abfb0 |
| Issue introduced in 6.3 with commit 7ff6edf4fef38ab404ee7861f257e28eaaeed35f and fixed in 6.12.20 with commit 488ffc0cac38f203979f83634236ee53251ce593 |
| Issue introduced in 6.3 with commit 7ff6edf4fef38ab404ee7861f257e28eaaeed35f and fixed in 6.13.8 with commit 5ac295dfccb5b015493f86694fa13a0dde4d3665 |
| Issue introduced in 6.3 with commit 7ff6edf4fef38ab404ee7861f257e28eaaeed35f and fixed in 6.14 with commit e3e89178a9f4a80092578af3ff3c8478f9187d59 |
| Issue introduced in 4.14.308 with commit d6353e2fc12c5b8f00f86efa30ed73d2da2f77be |
| Issue introduced in 4.19.276 with commit 1b1e0eb1d2971a686b9f7bdc146115bcefcbb960 |
| Issue introduced in 6.2.3 with commit eaf5dea1eb8c2928554b3ca717575cbe232b843c |
| |
| 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-2025-21991 |
| 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/kernel/cpu/microcode/amd.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/d509c4731090ebd9bbdb72c70a2d70003ae81f4f |
| https://git.kernel.org/stable/c/985a536e04bbfffb1770df43c6470f635a6b1073 |
| https://git.kernel.org/stable/c/18b5d857c6496b78ead2fd10001b81ae32d30cac |
| https://git.kernel.org/stable/c/ec52240622c4d218d0240079b7c1d3ec2328a9f4 |
| https://git.kernel.org/stable/c/e686349cc19e800dac8971929089ba5ff59abfb0 |
| https://git.kernel.org/stable/c/488ffc0cac38f203979f83634236ee53251ce593 |
| https://git.kernel.org/stable/c/5ac295dfccb5b015493f86694fa13a0dde4d3665 |
| https://git.kernel.org/stable/c/e3e89178a9f4a80092578af3ff3c8478f9187d59 |
