| 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-2024-35804: KVM: x86: Mark target gfn of emulated atomic instruction as dirty |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| KVM: x86: Mark target gfn of emulated atomic instruction as dirty |
| |
| When emulating an atomic access on behalf of the guest, mark the target |
| gfn dirty if the CMPXCHG by KVM is attempted and doesn't fault. This |
| fixes a bug where KVM effectively corrupts guest memory during live |
| migration by writing to guest memory without informing userspace that the |
| page is dirty. |
| |
| Marking the page dirty got unintentionally dropped when KVM's emulated |
| CMPXCHG was converted to do a user access. Before that, KVM explicitly |
| mapped the guest page into kernel memory, and marked the page dirty during |
| the unmap phase. |
| |
| Mark the page dirty even if the CMPXCHG fails, as the old data is written |
| back on failure, i.e. the page is still written. The value written is |
| guaranteed to be the same because the operation is atomic, but KVM's ABI |
| is that all writes are dirty logged regardless of the value written. And |
| more importantly, that's what KVM did before the buggy commit. |
| |
| Huge kudos to the folks on the Cc list (and many others), who did all the |
| actual work of triaging and debugging. |
| |
| base-commit: 6769ea8da8a93ed4630f1ce64df6aafcaabfce64 |
| |
| The Linux kernel CVE team has assigned CVE-2024-35804 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.15.58 with commit d97c0667c1e61ded6639117b4b9584a9c12b7e66 and fixed in 5.15.154 with commit a9bd6bb6f02bf7132c1ab192ba62bbfa52df7d66 |
| Issue introduced in 5.19 with commit 1c2361f667f3648855ceae25f1332c18413fdb9f and fixed in 6.1.84 with commit 726374dde5d608b15b9756bd52b6fc283fda7a06 |
| Issue introduced in 5.19 with commit 1c2361f667f3648855ceae25f1332c18413fdb9f and fixed in 6.6.24 with commit 9d1b22e573a3789ed1f32033ee709106993ba551 |
| Issue introduced in 5.19 with commit 1c2361f667f3648855ceae25f1332c18413fdb9f and fixed in 6.7.12 with commit 225d587a073584946c05c9b7651d637bd45c0c71 |
| Issue introduced in 5.19 with commit 1c2361f667f3648855ceae25f1332c18413fdb9f and fixed in 6.8 with commit 910c57dfa4d113aae6571c2a8b9ae8c430975902 |
| Issue introduced in 5.17.13 with commit b0f294103f4cf733e23d3f0c4e5fd58e42998921 |
| Issue introduced in 5.18.2 with commit e964665cc7ca13a16992b205fce63554b9efc78b |
| |
| 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-2024-35804 |
| 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/kvm/x86.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/a9bd6bb6f02bf7132c1ab192ba62bbfa52df7d66 |
| https://git.kernel.org/stable/c/726374dde5d608b15b9756bd52b6fc283fda7a06 |
| https://git.kernel.org/stable/c/9d1b22e573a3789ed1f32033ee709106993ba551 |
| https://git.kernel.org/stable/c/225d587a073584946c05c9b7651d637bd45c0c71 |
| https://git.kernel.org/stable/c/910c57dfa4d113aae6571c2a8b9ae8c430975902 |
