Ubuntu Server 18.04 LTS: USN-3816-1 Critical Kernel Patch

The kernel packages contain the Linux kernel, the core of any Linux operating system.
Security fixes:
* several flaws were found in the way the Linux kernel CIFS implementation handles Unicode strings. CIFS clients convert Unicode strings sent by a server to their local character sets, and then write those strings into memory. If a malicious server sent a long enough string, it could write past the end of the target memory region and corrupt other memory areas, possibly leading to a denial of service or privilege escalation on the client mounting the CIFS share. (CVE-2009-1439, CVE-2009-1633, Important)
* the Linux kernel Network File System daemon (nfsd) implementation did not drop the CAP_MKNOD capability when handling requests from local, unprivileged users. This flaw could possibly lead to an information leak or privilege escalation. (CVE-2009-1072, Moderate)
* Frank Filz reported the NFSv4 client was missing a file permission check for the execute bit in some situations. This could allow local, unprivileged users to run non-executable files on NFSv4 mounted file systems. (CVE-2009-1630, Moderate)
* a missing check was found in the hypervisor_callback() function in the Linux kernel provided by the kernel-xen package. This could cause a denial of service of a 32-bit guest if an application running in that guest accesses a certain memory location in the kernel. (CVE-2009-1758, Moderate)
* a flaw was found in the AGPGART driver. The agp_generic_alloc_page() and agp_generic_alloc_pages() functions did not zero out the memory pages they allocate, which may later be available to user-space processes. This flaw could possibly lead to an information leak. (CVE-2009-1192, Low)
Bug fixes:
* a race in the NFS client between destroying cached access rights and unmounting an NFS file system could have caused a system crash. "Busy inodes" messages may have been logged. (BZ#498653)
* nanosleep() could sleep several milliseconds less than the specified time on Intel Itanium®-based systems. (BZ#500349)
* LEDs for disk drives in AHCI mode may have displayed a fault state when there were no faults. (BZ#500120)
* ptrace_do_wait() reported tasks were stopped each time the process doing the trace called wait(), instead of reporting it once. (BZ#486945)
* epoll_wait() may have caused a system lockup and problems for applications. (BZ#497322)
* missing capabilities could possibly allow users with an fsuid other than 0 to perform actions on some file system types that would otherwise be prevented. (BZ#497271)
* on NFS mounted file systems, heavy write loads may have blocked nfs_getattr() for long periods, causing commands that use stat(2), such as ls, to hang. (BZ#486926)
* in rare circumstances, if an application performed multiple O_DIRECT reads per virtual memory page and also performed fork(2), the buffer storing the result of the I/O may have ended up with invalid data. (BZ#486921)
* when using GFS2, gfs2_quotad may have entered an uninterpretable sleep state. (BZ#501742)
* with this update, get_random_int() is more random and no longer uses a common seed value, reducing the possibility of predicting the values returned. (BZ#499783)
* the "-fwrapv" flag was added to the gcc build options to prevent gcc from optimizing away wrapping. (BZ#501751)
* a kernel panic when enabling and disabling iSCSI paths. (BZ#502916)
* using the Broadcom NetXtreme BCM5704 network device with the tg3 driver caused high system load and very bad performance. (BZ#502837)
* "/proc/[pid]/maps" and "/proc/[pid]/smaps" can only be read by processes able to use the ptrace() call on a given process; however, certain information from "/proc/[pid]/stat" and "/proc/[pid]/wchan" could be used to reconstruct memory maps. (BZ#499546)
Users should upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.