ELA-17-1 linux security update

Linux Kernel 3.16 security update

Related CVEs CVE-2017-5715 CVE-2017-5753 CVE-2018-1066 CVE-2018-1093 CVE-2018-1130 CVE-2018-3665 CVE-2018-5814 CVE-2018-9422 CVE-2018-10853 CVE-2018-10940 CVE-2018-11506 CVE-2018-12233 CVE-2018-1000204

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


Multiple researchers have discovered a vulnerability in various
processors supporting speculative execution, enabling an attacker
controlling an unprivileged process to read memory from arbitrary
addresses, including from the kernel and all other processes
running on the system.

This specific attack has been named Spectre variant 2 (branch
target injection) and is mitigated for the x86 architecture (amd64
and i386) by using new microcoded features.

This mitigation requires an update to the processor's microcode,
which is non-free. For recent Intel processors, this is included
in the intel-microcode package from version 3.20180703.2~bpo8+1~deb7u1.
For other processors, it may be included in an update to the
system BIOS or UEFI firmware, or in a later update to the
amd64-microcode package.

This vulnerability was already mitigated for the x86 architecture
by the "retpoline" feature.


Further instances of code that was vulnerable to Spectre variant 1
(bounds-check bypass) have been mitigated.


Dan Aloni reported to Red Hat that the CIFS client implementation
would dereference a null pointer if the server sent an invalid
response during NTLMSSP setup negotiation. This could be used by a
malicious server for denial of service.

The previously applied mitigation for this issue was not
appropriate for Linux 3.16 and has been replaced by an alternate


Wen Xu reported that a crafted ext4 filesystem image could trigger
an out-of-bounds read in the ext4_valid_block_bitmap() function. A
local user able to mount arbitrary filesystems could use this for
denial of service.


The syzbot software found that the DCCP implementation of
sendmsg() does not check the socket state, potentially leading
to a null pointer dereference.  A local user could use this to
cause a denial of service (crash).


Multiple researchers have discovered that some Intel x86
processors can speculatively read floating-point and vector
registers even when access to those registers is disabled.  The
Linux kernel's "lazy FPU" feature relies on that access control to
avoid saving and restoring those registers for tasks that do not
use them, and was enabled by default on x86 processors that do
not support the XSAVEOPT instruction.

If "lazy FPU" is enabled on one of the affected processors, an
attacker controlling an unprivileged process may be able to read
sensitive information from other users' processes or the kernel.
This specifically affects processors based on the "Nehalem" and
"Westemere" core designs.

This issue has been mitigated by disabling "lazy FPU" by default
on all x86 processors that support the FXSAVE and FXRSTOR
instructions, which includes all processors known to be affected
and most processors that perform speculative execution.  It can
also be mitigated by adding the kernel parameter: eagerfpu=on


Jakub Jirasek reported race conditions in the USB/IP host driver.
A malicious client could use this to cause a denial of service
(crash or memory corruption), and possibly to execute code, on a
USB/IP server.


It was reported that the futex() system call could be used by an
unprivileged user for privilege escalation.


Andy Lutomirski and Mika Penttilä reported that KVM for x86
processors did not perform a necessary privilege check when
emulating certain instructions.  This could be used by an
unprivileged user in a guest VM to escalate their privileges
within the guest.


Dan Carpenter reported that the optical disc driver (cdrom) does
not correctly validate the parameter to the CDROM_MEDIA_CHANGED
ioctl.  A user with access to a cdrom device could use this to
cause a denial of service (crash).


Piotr Gabriel Kosinski and Daniel Shapira reported that the
SCSI optical disc driver (sr) did not allocate a sufficiently
large buffer for sense data.  A user with access to a SCSI
optical disc device that can produce more than 64 bytes of
sense data could use this to cause a denial of service (crash
or memory corruption), and possibly for privilege escalation.


Shankara Pailoor reported that a crafted JFS filesystem image
could trigger a denial of service (memory corruption).  This
could possibly also be used for privilege escalation.


The syzbot software found that the SCSI generic driver (sg) would
in some circumstances allow reading data from uninitialised
buffers, which could include sensitive information from the kernel
or other tasks.  However, only privileged users with the
CAP_SYS_ADMIN or CAP_SYS_RAWIO capability were allowed to do this,
so this has little or no security impact.

For Debian 7 Wheezy, these problems have been fixed in version 3.16.57-2~deb7u2.

We recommend that you upgrade your linux packages.

Further information about Extended LTS security advisories can be found in the dedicated section of our website.