cybersecurity weakness CVE-2018-20856

Linux kernel: use after free via __blk_drain_queue

Synthesis of the vulnerability

An attacker can force the usage of a freed memory area via __blk_drain_queue() of the Linux kernel, in order to trigger a denial of service, and possibly to run code.
Severity of this bulletin: 2/4.
Creation date: 14/08/2019.
Références of this threat: CERTFR-2019-AVI-391, CERTFR-2019-AVI-392, CERTFR-2019-AVI-418, CERTFR-2019-AVI-419, CERTFR-2019-AVI-513, CVE-2018-20856, DLA-1885-1, DSA-4497-1, RHSA-2019:3055-01, RHSA-2019:3076-01, RHSA-2019:3089-01, RHSA-2019:3217-01, SSA:2019-226-01, SUSE-SU-2019:2263-1, SUSE-SU-2019:2299-1, USN-4094-1, USN-4116-1, USN-4118-1, VIGILANCE-VUL-30051.
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Description of the vulnerability

An attacker can force the usage of a freed memory area via __blk_drain_queue() of the Linux kernel, in order to trigger a denial of service, and possibly to run code.
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This security vulnerability impacts software or systems such as Debian, Linux, RHEL, Slackware, SUSE Linux Enterprise Desktop, SLES, Ubuntu.

Our Vigil@nce team determined that the severity of this computer weakness bulletin is medium.

The trust level is of type confirmed by the editor, with an origin of user shell.

An attacker with a expert ability can exploit this security note.

Solutions for this threat

Linux kernel: version 4.18.7.
The version 4.18.7 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: version 4.9.189.
The version 4.9.189 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: version 4.4.189.
The version 4.4.189 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: patch for __blk_drain_queue.
A patch is indicated in information sources.

Debian 8: new linux-4.9 packages.
New packages are available:
  Debian 8: linux-4.9 4.9.168-1+deb9u5~deb8u1

Debian 9/10: new linux packages.
New packages are available:
  Debian 9: linux 4.9.168-1+deb9u5
  Debian 10: linux 4.19.37-5+deb10u2

RHEL 7: new kernel-alt packages.
New packages are available:
  RHEL 7: kernel-alt 4.14.0-115.14.1.el7a

RHEL 7: new kernel packages.
New packages are available:
  RHEL 7: kernel 3.10.0-1062.4.1.el7

RHEL 7: new kernel-rt packages.
New packages are available:
  RHEL 7: kernel-rt 3.10.0-1062.4.1.rt56.1027.el7

RHEL 7: new kpatch-patch packages.
New packages are available:
  RHEL 7: kpatch-patch 3_10_0-1062-1-5.el7

Slackware 14.2: new kernel packages.
New packages are available:
  Slackware 14.2: kernel 4.4.189-*-1

SUSE LE 12 SP2: new kernel packages.
New packages are available:
  SUSE LE 12 SP2: kernel 4.4.121-92.120.1

SUSE LE 12 SP3: new kernel packages.
New packages are available:
  SUSE LE 12 SP3: kernel 4.4.180-94.103.1

Ubuntu 16.04: new linux-image-4.4.0 packages.
New packages are available:
  Ubuntu 16.04 LTS: linux-image-generic 4.4.0.161.169

Ubuntu 16/18: new linux-image-aws packages.
New packages are available:
  Ubuntu 16.04 LTS: linux-image-aws 4.15.0.1047.47
  Ubuntu 18.04 LTS: linux-image-aws 4.15.0.1047.46

Ubuntu: new linux-image-4.15.0 packages.
New packages are available:
  Ubuntu 16.04 LTS: linux-image-generic-hwe-16.04 4.15.0.58.79
  Ubuntu 18.04 LTS: linux-image-generic 4.15.0.58.60
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