Debian DLA-1731-2 : linux regression update (Spectre)
High Nessus Plugin ID 123420
SynopsisThe remote Debian host is missing a security update.
DescriptionThe linux update issued as DLA-1731-1 caused a regression in the vmxnet3 (VMware virtual network adapter) driver. This update corrects that regression, and an earlier regression in the CIFS network filesystem implementation introduced in DLA-1422-1. For reference the original advisory text follows.
Several vulnerabilities have been discovered in the Linux kernel that may lead to a privilege escalation, denial of service or information leaks.
A race condition was discovered in XFS that would result in a crash (BUG). A local user permitted to write to an XFS volume could use this for denial of service.
Further instances of code that was vulnerable to Spectre variant 1 (bounds-check bypass) have been mitigated.
A memory over-read was discovered in the keys subsystem's encrypted key type. A local user could use this for denial of service or possibly to read sensitive information.
Multiple researchers have discovered that Speculative Store Bypass (SSB), a feature implemented in many processors, could be used to read sensitive information from another context. In particular, code in a software sandbox may be able to read sensitive information from outside the sandbox. This issue is also known as Spectre variant 4.
This update fixes bugs in the mitigations for SSB for AMD processors.
The wil6210 wifi driver did not properly validate lengths in scan and connection requests, leading to a possible buffer overflow. On systems using this driver, a local user with the CAP_NET_ADMIN capability could use this for denial of service (memory corruption or crash) or potentially for privilege escalation.
The swiotlb subsystem printed kernel memory addresses to the system log, which could help a local attacker to exploit other vulnerabilities.
Team OWL337 reported possible integer overflows in the POSIX timer implementation. These might have some security impact.
Vasily Averin and Pavel Tikhomirov from Virtuozzo Kernel Team discovered that the cleancache memory management feature did not invalidate cached data for deleted files. On Xen guests using the tmem driver, local users could potentially read data from other users' deleted files if they were able to create new files on the same volume.
A flaw was found in the NFS 4.1 client implementation. Mounting NFS shares in multiple network namespaces at the same time could lead to a user-after-free. Local users might be able to use this for denial of service (memory corruption or crash) or possibly for privilege escalation.
This can be mitigated by disabling unprivileged users from creating user namespaces, which is the default in Debian.
Jann Horn reported that the /proc/*/stack files in procfs leaked sensitive data from the kernel. These files are now only readable by users with the CAP_SYS_ADMIN capability (usually only root)
Jann Horn reported a race condition in the virtual memory manager that can result in a process briefly having access to memory after it is freed and reallocated. A local user permitted to create containers could possibly exploit this for denial of service (memory corruption) or for privilege escalation.
Kanda Motohiro reported that XFS did not correctly handle some xattr (extended attribute) writes that require changing the disk format of the xattr. A user with access to an XFS volume could use this for denial of service.
It was discovered that the cdrom driver does not correctly validate the parameter to the CDROM_SELECT_DISC ioctl. A user with access to a cdrom device could use this to read sensitive information from the kernel or to cause a denial of service (crash).
Hui Peng and Mathias Payer discovered a use-after-free bug in the USB audio driver. A physically present attacker able to attach a specially designed USB device could use this for privilege escalation.
Hui Peng and Mathias Payer discovered a missing bounds check in the hso USB serial driver. A physically present user able to attach a specially designed USB device could use this to read sensitive information from the kernel or to cause a denial of service (crash).
Hui Peng and Mathias Payer discovered missing bounds checks in the USB core. A physically present attacker able to attach a specially designed USB device could use this to cause a denial of service (crash) or possibly for privilege escalation.
InfoSect reported an information leak in the AppleTalk IP/DDP implemntation. A local user with CAP_NET_ADMIN capability could use this to read sensitive information from the kernel.
Muyu Yu and Marcus Meissner reported that the CAN gateway implementation allowed the frame length to be modified, typically resulting in out-of-bounds memory-mapped I/O writes. On a system with CAN devices present, a local user with CAP_NET_ADMIN capability in the initial net namespace could use this to cause a crash (oops) or other hardware-dependent impact.
A potential infinite loop was discovered in the HID debugfs interface exposed under /sys/kernel/debug/hid. A user with access to these files could use this for denial of service.
This interface is only accessible to root by default, which fully mitigates the issue.
Jann Horn reported a use-after-free bug in KVM. A local user with access to /dev/kvm could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation.
Jim Mattson and Felix Wilhelm reported a user-after-free bug in KVM's nested VMX implementation. On systems with Intel CPUs, a local user with access to /dev/kvm could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation.
Nested VMX is disabled by default, which fully mitigates the issue.
Felix Wilhelm reported an information leak in KVM for x86. A local user with access to /dev/kvm could use this to read sensitive information from the kernel.
Jann Horn reported that privileged tasks could cause stack segments, including those in other processes, to grow downward to address 0. On systems lacking SMAP (x86) or PAN (ARM), this exacerbated other vulnerabilities: a NULL pointer dereference could be exploited for privilege escalation rather than only for denial of service.
For Debian 8 'Jessie', these problems have been fixed in version 3.16.64-1.
We recommend that you upgrade your linux 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.