(RHSA-2017:2778) Moderate: samba security, bug fix, and enhancement update

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)