| 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-2024-35801: x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD |
| |
| Commit 672365477ae8 ("x86/fpu: Update XFD state where required") and |
| commit 8bf26758ca96 ("x86/fpu: Add XFD state to fpstate") introduced a |
| per CPU variable xfd_state to keep the MSR_IA32_XFD value cached, in |
| order to avoid unnecessary writes to the MSR. |
| |
| On CPU hotplug MSR_IA32_XFD is reset to the init_fpstate.xfd, which |
| wipes out any stale state. But the per CPU cached xfd value is not |
| reset, which brings them out of sync. |
| |
| As a consequence a subsequent xfd_update_state() might fail to update |
| the MSR which in turn can result in XRSTOR raising a #NM in kernel |
| space, which crashes the kernel. |
| |
| To fix this, introduce xfd_set_state() to write xfd_state together |
| with MSR_IA32_XFD, and use it in all places that set MSR_IA32_XFD. |
| |
| The Linux kernel CVE team has assigned CVE-2024-35801 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.16 with commit 672365477ae8afca5a1cca98c1deb733235e4525 and fixed in 6.1.84 with commit 21c7c00dae55cb0e3810d5f9506b58f68475d41d |
| Issue introduced in 5.16 with commit 672365477ae8afca5a1cca98c1deb733235e4525 and fixed in 6.6.24 with commit 1acbca933313aa866e39996904c9aca4d435c4cd |
| Issue introduced in 5.16 with commit 672365477ae8afca5a1cca98c1deb733235e4525 and fixed in 6.7.12 with commit 92b0f04e937665bde5768f3fcc622dcce44413d8 |
| Issue introduced in 5.16 with commit 672365477ae8afca5a1cca98c1deb733235e4525 and fixed in 6.8.3 with commit b61e3b7055ac6edee4be071c52f48c26472d2624 |
| Issue introduced in 5.16 with commit 672365477ae8afca5a1cca98c1deb733235e4525 and fixed in 6.9 with commit 10e4b5166df9ff7a2d5316138ca668b42d004422 |
| |
| 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-2024-35801 |
| 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/fpu/xstate.c |
| arch/x86/kernel/fpu/xstate.h |
| |
| |
| 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/21c7c00dae55cb0e3810d5f9506b58f68475d41d |
| https://git.kernel.org/stable/c/1acbca933313aa866e39996904c9aca4d435c4cd |
| https://git.kernel.org/stable/c/92b0f04e937665bde5768f3fcc622dcce44413d8 |
| https://git.kernel.org/stable/c/b61e3b7055ac6edee4be071c52f48c26472d2624 |
| https://git.kernel.org/stable/c/10e4b5166df9ff7a2d5316138ca668b42d004422 |
