RHSA-2017:2778 - Security Advisory

Topic

An update for samba is now available for Red Hat Gluster Storage 3.3 for RHEL 6.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

Samba is an open-source implementation of the Server Message Block (SMB) protocol and the related Common Internet File System (CIFS) protocol, which allow PC-compatible machines to share files, printers, and various information.

Security Fix(es):

• A race condition was found in samba server. A malicious samba client could use this flaw to access files and directories in areas of the server file system not exported under the share definitions. (CVE-2017-2619)
• A flaw was found in the way Samba handled dangling symlinks. An authenticated malicious Samba client could use this flaw to cause the smbd daemon to enter an infinite loop and use an excessive amount of CPU and memory. (CVE-2017-9461)

Red Hat would like to thank the Samba project for reporting CVE-2017-2619. Upstream acknowledges Jann Horn (Google) as the original reporter of CVE-2017-2619.

Bug Fix(es):

• In the samba configuration, by default the 'posix locking' is enabled and 'stat cache' is disabled. Enabling 'posix locking' sends the file lock request to the bricks too, and disabling 'stat cache' blocks samba to cache certain information at the samba layer. This led to decrease in performance of SMB access of Red Hat Gluster Storage volumes

As a fix, the following two options are included in the samba configuration file:
posix locking = No
stat cache = Yes

Due to this, a slight improvement in the performance is observed. (BZ#1436265)

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing this update, the smb service will be restarted automatically.

Affected Products

• Red Hat Gluster Storage Server for On-premise 3 for RHEL 6 x86_64

Fixes

• BZ - 1334397 - Samba [RHEL6] : Upon smbd crash the log displays core dump path as /var/log/samba/cores/smbd but in actual the core is dumped in /var/log/cores
• BZ - 1426663 - [RHEL6] Samba: Yum update for Samba will fail due to higher versions in RHEL 6
• BZ - 1429472 - CVE-2017-2619 samba: symlink race permits opening files outside share directory
• BZ - 1436265 - Smb.conf options for performance improvements [RHEL6]
• BZ - 1444028 - [SAMBA-RHEL6]Unable to start smbd in RHEL6 as /run/smbd.pid does not exist
• BZ - 1459464 - CVE-2017-9461 samba: fd_open_atomic infinite loop due to wrong handling of dangling symlinks

CVEs

• CVE-2017-2619
• CVE-2017-9461

References

• https://access.redhat.com/security/updates/classification/#moderate