| 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-2025-21818: x86/xen: fix xen_hypercall_hvm() to not clobber %rbx |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| x86/xen: fix xen_hypercall_hvm() to not clobber %rbx |
| |
| xen_hypercall_hvm(), which is used when running as a Xen PVH guest at |
| most only once during early boot, is clobbering %rbx. Depending on |
| whether the caller relies on %rbx to be preserved across the call or |
| not, this clobbering might result in an early crash of the system. |
| |
| This can be avoided by using an already saved register instead of %rbx. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21818 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.1.121 with commit 7e44e7065263c3baf287e7ff267a610cccde7544 and fixed in 6.1.129 with commit 522d726824cc570e0b6bf0b3af4d5a826f1b17c5 |
| Issue introduced in 6.6.67 with commit 31f29270c15bef700cbea40297c6b9a7114b3960 and fixed in 6.6.78 with commit 242f7584da3ad041a9db809d33d27a8be8eccc29 |
| Issue introduced in 6.12.6 with commit 3fbfac0f30441725e87d85d8629fa9dbc673704b and fixed in 6.12.14 with commit 4890a0858c09d96f3234a8f94663de80a7201bc4 |
| Issue introduced in 6.13 with commit b4845bb6383821a9516ce30af3a27dc873e37fd4 and fixed in 6.13.3 with commit 23f6f420cd727d641f95478fcf3bbbee41e4e5d6 |
| Issue introduced in 6.13 with commit b4845bb6383821a9516ce30af3a27dc873e37fd4 and fixed in 6.14-rc2 with commit 98a5cfd2320966f40fe049a9855f8787f0126825 |
| Issue introduced in 5.10.232 with commit 76b42b1340ca0c17961a1000474a23eff6f15f83 |
| Issue introduced in 5.15.175 with commit a501b4dbedb4cdcfa2372b40e6b405e26d3e8069 |
| |
| 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-2025-21818 |
| 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/xen/xen-head.S |
| |
| |
| 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/522d726824cc570e0b6bf0b3af4d5a826f1b17c5 |
| https://git.kernel.org/stable/c/242f7584da3ad041a9db809d33d27a8be8eccc29 |
| https://git.kernel.org/stable/c/4890a0858c09d96f3234a8f94663de80a7201bc4 |
| https://git.kernel.org/stable/c/23f6f420cd727d641f95478fcf3bbbee41e4e5d6 |
| https://git.kernel.org/stable/c/98a5cfd2320966f40fe049a9855f8787f0126825 |
