| 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-2021-47450: KVM: arm64: Fix host stage-2 PGD refcount |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| KVM: arm64: Fix host stage-2 PGD refcount |
| |
| The KVM page-table library refcounts the pages of concatenated stage-2 |
| PGDs individually. However, when running KVM in protected mode, the |
| host's stage-2 PGD is currently managed by EL2 as a single high-order |
| compound page, which can cause the refcount of the tail pages to reach 0 |
| when they shouldn't, hence corrupting the page-table. |
| |
| Fix this by introducing a new hyp_split_page() helper in the EL2 page |
| allocator (matching the kernel's split_page() function), and make use of |
| it from host_s2_zalloc_pages_exact(). |
| |
| The Linux kernel CVE team has assigned CVE-2021-47450 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.13 with commit 1025c8c0c6accfcbdc8f52ca1940160f65cd87d6 and fixed in 5.14.15 with commit b372264c66ef78f2cab44e877fbd765ad6d24c39 |
| Issue introduced in 5.13 with commit 1025c8c0c6accfcbdc8f52ca1940160f65cd87d6 and fixed in 5.15 with commit 1d58a17ef54599506d44c45ac95be27273a4d2b1 |
| |
| 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-2021-47450 |
| 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/arm64/kvm/hyp/include/nvhe/gfp.h |
| arch/arm64/kvm/hyp/nvhe/mem_protect.c |
| arch/arm64/kvm/hyp/nvhe/page_alloc.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/b372264c66ef78f2cab44e877fbd765ad6d24c39 |
| https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1 |
