CVSS: 6.5EPSS: 0%CPEs: 5EXPL: 1CVE-2020-8834 – Linux kernel KVM Power8 conflicting use of HSTATE_HOST_R1
https://notcve.org/view.php?id=CVE-2020-8834
KVM in the Linux kernel on Power8 processors has a conflicting use of HSTATE_HOST_R1 to store r1 state in kvmppc_hv_entry plus in kvmppc_{save,restore}_tm, leading to a stack corruption. Because of this, an attacker with the ability run code in kernel space of a guest VM can cause the host kernel to panic. There were two commits that, according to the reporter, introduced the vulnerability: f024ee098476 ("KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures") 87a11bb6a7f7 ("KVM: PPC: Book3S HV: Work around XER[SO] bug in fake suspend mode") The former landed in 4.8, the latter in 4.17. This was fixed without realizing the impact in 4.18 with the following three commits, though it's believed the first is the only strictly necessary commit: 6f597c6b63b6 ("KVM: PPC: Book3S PR: Add guest MSR parameter for kvmppc_save_tm()/kvmppc_restore_tm()") 7b0e827c6970 ("KVM: PPC: Book3S HV: Factor fake-suspend handling out of kvmppc_save/restore_tm") 009c872a8bc4 ("KVM: PPC: Book3S PR: Move kvmppc_save_tm/kvmppc_restore_tm to separate file") KVM en el kernel de Linux en los procesadores Power8, presenta un uso conflictivo de HSTATE_HOST_R1 para almacenar el estado r1 en plus kvmppc_hv_entry en kvmppc_ {save, restore} _tm, conllevando a una corrupción de la pila. Debido a esto, un atacante con la capacidad de ejecutar código en el espacio del kernel de una Máquina Virtual invitada puede causar que el kernel del host entre en pánico. • http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00035.html https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1867717 https://usn.ubuntu.com/4318-1 https://usn.ubuntu.com/usn/usn-4318-1 https://www.openwall.com/lists/oss-security/2020/04/06/2 https://access.redhat.com/security/cve/CVE-2020-8834 https://bugzilla.redhat.com/show_bug.cgi?id=1819615 • CWE-121: Stack-based Buffer Overflow CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') CWE-368: Context Switching Race Condition •
CVSS: 6.6EPSS: 0%CPEs: 3EXPL: 0CVE-2017-1000255 – kernel: Arbitrary stack overwrite causing oops via crafted signal frame
https://notcve.org/view.php?id=CVE-2017-1000255
On Linux running on PowerPC hardware (Power8 or later) a user process can craft a signal frame and then do a sigreturn so that the kernel will take an exception (interrupt), and use the r1 value *from the signal frame* as the kernel stack pointer. As part of the exception entry the content of the signal frame is written to the kernel stack, allowing an attacker to overwrite arbitrary locations with arbitrary values. The exception handling does produce an oops, and a panic if panic_on_oops=1, but only after kernel memory has been over written. This flaw was introduced in commit: "5d176f751ee3 (powerpc: tm: Enable transactional memory (TM) lazily for userspace)" which was merged upstream into v4.9-rc1. Please note that kernels built with CONFIG_PPC_TRANSACTIONAL_MEM=n are not vulnerable. • http://www.securityfocus.com/bid/101264 https://access.redhat.com/errata/RHSA-2018:0654 https://access.redhat.com/security/cve/CVE-2017-1000255 https://bugzilla.redhat.com/show_bug.cgi?id=1498067 • CWE-787: Out-of-bounds Write •