SynopsisThe remote Debian host is missing a security update.
DescriptionSeveral vulnerabilities have been discovered in the Linux kernel that may lead to a privilege escalation, denial of service or information leaks.
Denis Andzakovic reported a missing type check in the IPv4 multicast routing implementation. A user with the CAP_NET_ADMIN capability (in any user namespace) could use this for denial of service (memory corruption or crash) or possibly for privilege escalation.
ADLab of VenusTech discovered that the kernel logged the virtual addresses assigned to per-CPU data, which could make it easier to exploit other vulnerabilities.
chenxiang reported a race condition in libsas, the kernel subsystem supporting Serial Attached SCSI (SAS) devices, which could lead to a use-after-free. It is not clear how this might be exploited.
Xiao Jin reported a potential double-free in the block subsystem, in case an error occurs while initialising the I/O scheduler for a block device. It is not clear how this might be exploited.
It was discovered that most x86 processors could speculatively skip a conditional SWAPGS instruction used when entering the kernel from user mode, and/or could speculatively execute it when it should be skipped.
This is a subtype of Spectre variant 1, which could allow local users to obtain sensitive information from the kernel or other processes. It has been mitigated by using memory barriers to limit speculative execution. Systems using an i386 kernel are not affected as the kernel does not use SWAPGS.
It was found that the vfio implementation did not limit the number of DMA mappings to device memory. A local user granted ownership of a vfio device could use this to cause a denial of service (out-of-memory condition).
It was discovered that vhost drivers did not properly control the amount of work done to service requests from guest VMs. A malicious guest could use this to cause a denial of service (unbounded CPU usage) on the host.
The syzkaller tool found a potential null dereference in various drivers for UART-attached Bluetooth adapters. A local user with access to a pty device or other suitable tty device could use this for denial of service (BUG/oops).
Amit Klein and Benny Pinkas discovered that the generation of IP packet IDs used a weak hash function, 'jhash'. This could enable tracking individual computers as they communicate with different remote servers and from different networks. The 'siphash' function is now used instead.
Amit Klein and Benny Pinkas discovered that the generation of IP packet IDs used a weak hash function that incorporated a kernel virtual address. This hash function is no longer used for IP IDs, although it is still used for other purposes in the network stack.
It was discovered that the gtco driver for USB input tablets could overrun a stack buffer with constant data while parsing the device's descriptor. A physically present user with a specially constructed USB device could use this to cause a denial of service (BUG/oops), or possibly for privilege escalation.
Praveen Pandey reported that on PowerPC (ppc64el) systems without Transactional Memory (TM), the kernel would still attempt to restore TM state passed to the sigreturn() system call. A local user could use this for denial of service (oops).
The syzkaller tool found a missing bounds check in the floppy disk driver. A local user with access to a floppy disk device, with a disk present, could use this to read kernel memory beyond the I/O buffer, possibly obtaining sensitive information.
The syzkaller tool found a potential division-by-zero in the floppy disk driver. A local user with access to a floppy disk device could use this for denial of service (oops).
(CVE ID not yet assigned)
Denis Andzakovic reported a possible use-after-free in the TCP sockets implementation. A local user could use this for denial of service (memory corruption or crash) or possibly for privilege escalation.
(CVE ID not yet assigned)
The netfilter conntrack subsystem used kernel addresses as user-visible IDs, which could make it easier to exploit other security vulnerabilities.
Julien Grall reported that Linux does not limit the amount of memory which a domain will attempt to baloon out, nor limits the amount of 'foreign / grant map' memory which any individual guest can consume, leading to denial of service conditions (for host or guests).
For Debian 8 'Jessie', these problems have been fixed in version 4.9.168-1+deb9u5~deb8u1.
We recommend that you upgrade your linux-4.9 packages.
NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
SolutionUpgrade the affected packages.