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.

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.

hw: cpu: speculative execution bounds-check bypass kernel: Buffer overflow in mp_override_legacy_irq() kernel: memory leak when merging buffers in SCSI IO vectors kernel: NULL pointer dereference due to KEYCTL_READ on negative key kernel: net: double-free and memory corruption in get_net_ns_by_id() kernel: Incorrect updates of uninstantiated keys crash the kernel Kernel: KVM: oops when checking KVM_CAP_PPC_HTM on PPC platform Kernel: ipsec: xfrm: use-after-free leading to potential privilege escalation kernel: Missing capabilities check in net/netfilter/nfnetlink_cthelper.c allows for unprivileged access to systemwide nfnl_cthelper_list structure kernel: Missing namespace check in net/netlink/af_netlink.c allows for network monitors to observe systemwide activity kernel: Arbitrary stack overwrite causing oops via crafted signal frame kernel: Stack information leak in the EFS element kernel: Integer overflow in futex.c:futux_requeue can lead to denial of service or unspecified impact kernel: Race condition in sound system can lead to denial of service

Affected: Ubuntu:16.04:LTS: linux-hwe

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.