Debian DLA-1422-2 : linux security update (Spectre)
High Nessus Plugin ID 111082
SynopsisThe remote Debian host is missing a security update.
DescriptionThe previous update to linux failed to build for the armhf (ARM EABI hard-float) architecture. This update corrects that. For all other architectures, there is no need to upgrade or reboot again. For reference, the relevant part of 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.
Multiple researchers have discovered a vulnerability in various processors supporting speculative execution, enabling an attacker controlling an unprivileged process to read memory from arbitrary addresses, including from the kernel and all other processes running on the system.
This specific attack has been named Spectre variant 2 (branch target injection) and is mitigated for the x86 architecture (amd64 and i386) by using new microcoded features.
This mitigation requires an update to the processor's microcode, which is non-free. For recent Intel processors, this is included in the intel-microcode package from version 3.20180425.1~deb8u1. For other processors, it may be included in an update to the system BIOS or UEFI firmware, or in a later update to the amd64-microcode package.
This vulnerability was already mitigated for the x86 architecture by the 'retpoline' feature.
Further instances of code that was vulnerable to Spectre variant 1 (bounds-check bypass) have been mitigated.
Dan Aloni reported to Red Hat that the CIFS client implementation would dereference a NULL pointer if the server sent an invalid response during NTLMSSP setup negotiation. This could be used by a malicious server for denial of service.
The previously applied mitigation for this issue was not appropriate for Linux 3.16 and has been replaced by an alternate fix.
Wen Xu reported that a crafted ext4 filesystem image could trigger an out-of-bounds read in the ext4_valid_block_bitmap() function. A local user able to mount arbitrary filesystems could use this for denial of service.
The syzbot software found that the DCCP implementation of sendmsg() does not check the socket state, potentially leading to a NULL pointer dereference. A local user could use this to cause a denial of service (crash).
Multiple researchers have discovered that some Intel x86 processors can speculatively read floating-point and vector registers even when access to those registers is disabled. The Linux kernel's 'lazy FPU' feature relies on that access control to avoid saving and restoring those registers for tasks that do not use them, and was enabled by default on x86 processors that do not support the XSAVEOPT instruction.
If 'lazy FPU' is enabled on one of the affected processors, an attacker controlling an unprivileged process may be able to read sensitive information from other users' processes or the kernel. This specifically affects processors based on the 'Nehalem' and 'Westemere' core designs. This issue has been mitigated by disabling 'lazy FPU' by default on all x86 processors that support the FXSAVE and FXRSTOR instructions, which includes all processors known to be affected and most processors that perform speculative execution. It can also be mitigated by adding the kernel parameter: eagerfpu=on
Jakub Jirasek reported race conditions in the USB/IP host driver. A malicious client could use this to cause a denial of service (crash or memory corruption), and possibly to execute code, on a USB/IP server.
It was reported that the futex() system call could be used by an unprivileged user for privilege escalation.
Andy Lutomirski and Mika Penttilä reported that KVM for x86 processors did not perform a necessary privilege check when emulating certain instructions. This could be used by an unprivileged user in a guest VM to escalate their privileges within the guest.
Dan Carpenter reported that the optical disc driver (cdrom) does not correctly validate the parameter to the CDROM_MEDIA_CHANGED ioctl. A user with access to a cdrom device could use this to cause a denial of service (crash).
Piotr Gabriel Kosinski and Daniel Shapira reported that the SCSI optical disc driver (sr) did not allocate a sufficiently large buffer for sense data. A user with access to a SCSI optical disc device that can produce more than 64 bytes of sense data could use this to cause a denial of service (crash or memory corruption), and possibly for privilege escalation.
Shankara Pailoor reported that a crafted JFS filesystem image could trigger a denial of service (memory corruption). This could possibly also be used for privilege escalation.
The syzbot software found that the SCSI generic driver (sg) would in some circumstances allow reading data from uninitialised buffers, which could include sensitive information from the kernel or other tasks. However, only privileged users with the CAP_SYS_ADMIN or CAP_SYS_RAWIO capability were allowed to do this, so this has little or no security impact.
For Debian 8 'Jessie', these problems have been fixed in version 3.16.57-1. This update additionally fixes Debian bug #898165, and includes many more bug fixes from stable update 3.16.57.
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.