MGASA-2017-0383

This kernel-linus update is based on upstream 4.9.56 and fixes at least the following security issues:

A flaw was found in the way the Linux KVM module processed the trap flag(TF) bit in EFLAGS during emulation of the syscall instruction, which leads to a debug exception(#DB) being raised in the guest stack. A user/process inside a guest could use this flaw to potentially escalate their privileges inside the guest (CVE-2017-7518).

A kernel data leak due to an out-of-bound read was found in the Linux kernel in inet_diag_msg_sctp{,l}addr_fill() and sctp_get_sctp_info() functions present since version 4.7-rc1 through version 4.13. A data leak happens when these functions fill in sockaddr data structures used to export socket's diagnostic information. As a result, up to 100 bytes of the slab data could be leaked to a userspace (CVE-2017-7558).

A security flaw was discovered in nl80211_set_rekey_data() function in the Linux kernel since v3.1-rc1 through v4.13. This function does not check whether the required attributes are present in a netlink request. This request can be issued by a user with CAP_NET_ADMIN privilege and may result in NULL dereference and a system crash (CVE-2017-12153).

Linux kernel built with the KVM visualization support (CONFIG_KVM), with nested visualization (nVMX) feature enabled (nested=1), is vulnerable to a crash due to disabled external interrupts. As L2 guest could acce s (r/w) hardware CR8 register of the host(L0). In a nested visualization setup, L2 guest user could use this flaw to potentially crash the host(L0) resulting in DoS (CVE-2017-12154).

The tcp_disconnect function in net/ipv4/tcp.c in the Linux kernel before 4.12 allows local users to cause a denial of service (__tcp_select_window divide-by-zero error and system crash) by triggering a disconnect within a certain tcp_recvmsg code path (CVE-2017-14106).

The atyfb_ioctl function in drivers/video/fbdev/aty/atyfb_base.c in the Linux kernel through 4.12.10 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel stack memory by reading locations associated with padding bytes (CVE-2017-14156).

It was found that the iscsi_if_rx() function in scsi_transport_iscsi.c in the Linux kernel since v2.6.24-rc1 through 4.13.2 allows local users to cause a denial of service (a system panic) by making a number of certain syscalls by leveraging incorrect length validation in the kernel code (CVE-2017-14489).

The sg_ioctl function in drivers/scsi/sg.c in the Linux kernel before 4.13.4 allows local users to obtain sensitive information from uninitialized kernel heap-memory locations via an SG_GET_REQUEST_TABLE ioctl call for /dev/sg0 (CVE-2017-14991).

The tpacket_rcv() function in 'net/packet/af_packet.c' file in the Linux kernel before 4.13 mishandles vnet headers, which might allow local users to cause a denial of service (buffer overflow, and disk and memory corruption) or possibly have unspecified other impact via crafted system calls (CVE-2017-14497).

A reachable assertion failure flaw was found in the Linux kernel built with KVM virtualisation(CONFIG_KVM) support with Virtual Function I/O feature (CONFIG_VFIO) enabled. This failure could occur if a malicious guest device sent a virtual interrupt (guest IRQ) with a larger (>1024) index value (CVE-2017-1000252).

For other upstream fixes in this update, read the referenced changelogs.