ELA-339-1 linux-4.9 security update

linux kernel update

2020-12-30
Packagelinux-4.9
Version4.9.246-2~deb8u1
Related CVEs CVE-2020-0427 CVE-2020-8694 CVE-2020-14351 CVE-2020-25645 CVE-2020-25656 CVE-2020-25668 CVE-2020-25669 CVE-2020-25704 CVE-2020-25705 CVE-2020-27673 CVE-2020-27675 CVE-2020-28974

Several vulnerabilities have been discovered in the Linux kernel that may lead to the execution of arbitrary code, privilege escalation, denial of service or information leaks.

CVE-2020-0427

Elena Petrova reported a bug in the pinctrl subsystem that can
lead to a use-after-free after a device is renamed.  The security
impact of this is unclear.

CVE-2020-8694

Multiple researchers discovered that the powercap subsystem
allowed all users to read CPU energy meters, by default.  On
systems using Intel CPUs, this provided a side channel that could
leak sensitive information between user processes, or from the
kernel to user processes.  The energy meters are now readable only
by root, by default.

This issue can be mitigated by running:

    chmod go-r /sys/devices/virtual/powercap/*/*/energy_uj

This needs to be repeated each time the system is booted with
an unfixed kernel version.

CVE-2020-14351

A race condition was discovered in the performance events
subsystem, which could lead to a use-after-free.  A local user
permitted to access performance events could use this to cause a
denial of service (crash or memory corruption) or possibly for
privilege escalation.

Debian's kernel configuration does not allow unprivileged users to
access peformance events by default, which fully mitigates this
issue.

CVE-2020-25645

A flaw was discovered in the interface driver for GENEVE
encapsulated traffic when combined with IPsec. If IPsec is
configured to encrypt traffic for the specific UDP port used by the
GENEVE tunnel, tunneled data isn't correctly routed over the
encrypted link and sent unencrypted instead.

CVE-2020-25656

Yuan Ming and Bodong Zhao discovered a race condition in the
virtual terminal (vt) driver that could lead to a use-after-free.
A local user with the CAP_SYS_TTY_CONFIG capability could use this
to cause a denial of service (crash or memory corruption) or
possibly for privilege escalation.

CVE-2020-25668

Yuan Ming and Bodong Zhao discovered a race condition in the
virtual terminal (vt) driver that could lead to a use-after-free.
A local user with access to a virtual terminal, or with the
CAP_SYS_TTY_CONFIG capability, could use this to cause a denial of
service (crash or memory corruption) or possibly for privilege
escalation.

CVE-2020-25669

Bodong Zhao discovered a bug in the Sun keyboard driver (sunkbd)
that could lead to a use-after-free.  On a system using this
driver, a local user could use this to cause a denial of service
(crash or memory corruption) or possibly for privilege escalation.

CVE-2020-25704

kiyin(尹亮) discovered a potential memory leak in the performance
events subsystem.  A local user permitted to access performance
events could use this to cause a denial of service (memory
exhaustion).

Debian's kernel configuration does not allow unprivileged users to
access peformance events by default, which fully mitigates this
issue.

CVE-2020-25705

Keyu Man reported that strict rate-limiting of ICMP packet
transmission provided a side-channel that could help networked
attackers to carry out packet spoofing.  In particular, this made
it practical for off-path networked attackers to "poison" DNS
caches with spoofed responses ("SAD DNS" attack).

This issue has been mitigated by randomising whether packets are
counted against the rate limit.

CVE-2020-27673 / XSA-332

Julien Grall from Arm discovered a bug in the Xen event handling
code.  Where Linux was used in a Xen dom0, unprivileged (domU)
guests could cause a denial of service (excessive CPU usage or
hang) in dom0.

CVE-2020-27675 / XSA-331

Jinoh Kang of Theori discovered a race condition in the Xen event
handling code.  Where Linux was used in a Xen dom0, unprivileged
(domU) guests could cause a denial of service (crash) in dom0.

CVE-2020-28974

Yuan Ming discovered a bug in the virtual terminal (vt) driver
that could lead to an out-of-bounds read.  A local user with
access to a virtual terminal, or with the CAP_SYS_TTY_CONFIG
capability, could possibly use this to obtain sensitive
information from the kernel or to cause a denial of service
(crash).

The specific ioctl operation affected by this bug
(KD_FONT_OP_COPY) has been disabled, as it is not believed that
any programs depended on it.

For Debian 8 jessie, these problems have been fixed in version 4.9.246-2~deb8u1.

We recommend that you upgrade your linux-4.9 packages.

Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/