Advisories » MGASA-2021-0100

Updated kernel-linus packages fix security vulnerabilities

Publication date: 04 Mar 2021
Type: security
Affected Mageia releases : 7
CVE: CVE-2021-20194 , CVE-2021-21781 , CVE-2021-26930 , CVE-2021-26931 , CVE-2021-26932


This kernel-linus update is based on upstream 5.10.19 and fixes at least
the following security issues:

There is a vulnerability in the linux kernel versions higher than 5.2 (if
kernel compiled with config params CONFIG_BPF_SYSCALL=y, CONFIG_BPF=y,
and BPF hook to getsockopt is registered). As result of BPF execution,
the local user can trigger bug in __cgroup_bpf_run_filter_getsockopt()
function that can lead to heap overflow (because of non-hardened
usercopy). The impact of attack could be deny of service or possibly
privileges escalation. NOTE! Mageia kernel configs have HARDENED_USERCOPY
enabled by default, making this an non-issue when using prebuilt kernels

An information disclosure vulnerability exists in the ARM SIGPAGE
functionality of Linux Kernel. A userland application can read the
contents of the sigpage, which can leak kernel memory contents. An
attacker can read a process’s memory at a specific offset to trigger
this vulnerability (CVE-2021-21781).

An issue was discovered in the Linux kernel 3.11 through 5.10.16, as used
by Xen. To service requests to the PV backend, the driver maps grant
references provided by the frontend. In this process, errors may be
encountered. In one case, an error encountered earlier might be
discarded by later processing, resulting in the caller assuming
successful mapping, and hence subsequent operations trying to access
space that wasn't mapped. In another case, internal state would be
insufficiently updated, preventing safe recovery from the error

An issue was discovered in the Linux kernel 2.6.39 through 5.10.16, as
used in Xen. Block, net, and SCSI backends consider certain errors a
plain bug, deliberately causing a kernel crash. For errors potentially
being at least under the influence of guests (such as out of memory
conditions), it isn't correct to assume a plain bug. Memory allocations
potentially causing such crashes occur only when Linux is running in
PV mode, though (CVE-2021-26931).

An issue was discovered in the Linux kernel 3.2 through 5.10.16, as used
by Xen. Grant mapping operations often occur in batch hypercalls, where
a number of operations are done in a single hypercall, the success or
failure of each one is reported to the backend driver, and the backend
driver then loops over the results, performing follow-up actions based
on the success or failure of each operation. Unfortunately, when running
in PV mode, the Linux backend drivers mishandle this: Some errors are
ignored, effectively implying their success from the success of related
batch elements. In other cases, errors resulting from one batch element
lead to further batch elements not being inspected, and hence successful
ones to not be possible to properly unmap upon error recovery. Only
systems with Linux backends running in PV mode are vulnerable. Linux
backends run in HVM / PVH modes are not vulnerable (CVE-2021-26932).

It also adds the following fixes:
- enable ACPI_EC_DEBUGFS (mga#28415)

For other upstream fixes, see the referenced changelogs.