CVE-2020-8835

In the Linux kernel 5.5.0 and newer, the bpf verifier (kernel/bpf/verifier.c) did not properly restrict the register bounds for 32-bit operations, leading to out-of-bounds reads and writes in kernel memory. The vulnerability also affects the Linux 5.4 stable series, starting with v5.4.7, as the introducing commit was backported to that branch. This vulnerability was fixed in 5.6.1, 5.5.14, and 5.4.29. (issue is aka ZDI-CAN-10780)

In the Linux kernel 5.5.0 and newer, the bpf verifier (kernel/bpf/verifier.c) did not properly restrict the register bounds for 32-bit operations, leading to out-of-bounds reads and writes in kernel memory. The vulnerability also affects the Linux 5.4 stable series, starting with v5.4.7, as the introducing commit was backported to that branch. This vulnerability was fixed in 5.6.1, 5.5.14, and 5.4.29. (issue is aka ZDI-CAN-10780)

This update is based on upstream 5.5.14 and fixes at least the following security vulnerabilities:

In the Linux kernel 5.3.10, there is a use-after-free (read) in the perf_trace_lock_acquire function (related to include/trace/events/lock.h) (CVE-2019-19769).

Manfred Paul discovered that the bpf verifier in the Linux kernel did not properly calculate register bounds for certain operations. A local attacker could use this to expose sensitive information (kernel memory) or gain administrative privileges (CVE-2020-8835).

Security fixes and hardenings to the mac00211 layer to prevent leaking keys and frames.

Other notable changes in this update:

• WireGuard kernel module has been updated to v1.0.20200330 and the tools to v1.0.20200319.
• exfat-utils has been rebuilt in core (was previously in tainted) as we now also ship the official upstream exfat driver.

For other upstream fixes in this update, see the referenced changelogs.

This update is based on upstream 5.5.15 and fixes at least the following security vulnerabilities:

In the Linux kernel 5.4.0-rc2, there is a use-after-free (read) in the __blk_add_trace function in kernel/trace/blktrace.c (which is used to fill out a blk_io_trace structure and place it in a per-cpu sub-buffer) (CVE-2019-19768).

In the Linux kernel 5.3.10, there is a use-after-free (read) in the perf_trace_lock_acquire function (related to include/trace/events/lock.h) (CVE-2019-19769).

A flaw was found in the way KVM hypervisor handled instruction emulation for the L2 guest when nested(=1) virtualization is enabled. In the instruction emulation, the L2 guest could trick the L0 hypervisor into accessing sensitive bits of the L1 hypervisor. An L2 guest could use this flaw to potentially access information of the L1 hypervisor (CVE-2020-2732).

There is a use-after-free vulnerability in the Linux kernel through 5.5.2 in the vc_do_resize function in drivers/tty/vt/vt.c (CVE-2020-8647).

There is a use-after-free vulnerability in the Linux kernel through 5.5.2 in the n_tty_receive_buf_common function in drivers/tty/n_tty.c (CVE-2020-8648).

Manfred Paul discovered that the bpf verifier in the Linux kernel did not properly calculate register bounds for certain operations. A local attacker could use this to expose sensitive information (kernel memory) or gain administrative privileges (CVE-2020-8835).

There is a use-after-free vulnerability in the Linux kernel through 5.5.2 in the vgacon_invert_region function in drivers/video/console/vgacon.c. (CVE-2020-8649).

An issue was discovered in the Linux kernel through 5.5.6. set_fdc in drivers/block/floppy.c leads to a wait_til_ready out-of-bounds read because the FDC index is not checked for errors before assigning it, aka CID-2e90ca68b0d2 (CVE-2020-9383).

An issue was discovered in the Linux kernel 5.4 and 5.5 through 5.5.6 on the AArch64 architecture. It ignores the top byte in the address passed to the brk system call, potentially moving the memory break downwards when the application expects it to move upwards, aka CID- dcde237319e6. This has been observed to cause heap corruption with the GNU C Library malloc implementation (CVE-2020-9391).

Security fixes and hardenings to the mac00211 layer to prevent leaking keys and frames.

For other upstream fixes in this update, see the referenced changelogs.

Manfred Paul discovered that the bpf verifier in the Linux kernel did not properly calculate register bounds for certain operations. A local attacker could use this to expose sensitive information (kernel memory) or gain administrative privileges.