Bug 1951595 (CVE-2021-29155) - CVE-2021-29155 kernel: protection for sequences of pointer arithmetic operations against speculatively out-of-bounds loads can be bypassed to leak content of kernel memory
Summary: CVE-2021-29155 kernel: protection for sequences of pointer arithmetic operati...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-29155
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1961563 1961564 1961565 1961566 1951597 1960942 1960943 1960944 1960945
Blocks: 1951598
TreeView+ depends on / blocked
 
Reported: 2021-04-20 14:29 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-11-09 20:24 UTC (History)
41 users (show)

Fixed In Version: Kernel 5.12
Doc Type: If docs needed, set a value
Doc Text:
A vulnerability was discovered in retrieve_ptr_limit in kernel/bpf/verifier.c in the Linux kernel mechanism to mitigate speculatively out-of-bounds loads (Spectre mitigation). In this flaw a local, special user privileged (CAP_SYS_ADMIN) BPF program running on affected systems may bypass the protection, and execute speculatively out-of-bounds loads from the kernel memory. This can be abused to extract contents of kernel memory via side-channel.
Clone Of:
Environment:
Last Closed: 2021-11-09 20:24:28 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:4140 0 None None None 2021-11-09 17:22:21 UTC
Red Hat Product Errata RHSA-2021:4356 0 None None None 2021-11-09 18:25:04 UTC

Description Guilherme de Almeida Suckevicz 2021-04-20 14:29:12 UTC 
A vulnerability was discovered in retrieve_ptr_limit in kernel/bpf/verifier.c in the Linux kernel mechanism to mitigate speculatively out-of-bounds loads (Spectre mitigation). In this flaw a local, special user privileged (CAP_SYS_ADMIN) BPF programs running on affected systems can bypass the protection and execute speculatively out-of-bounds loads from the kernel memory. This can be abused to extract contents of kernel memory via side-channel.

Reference:
https://www.openwall.com/lists/oss-security/2021/04/18/4
Comment 1 Guilherme de Almeida Suckevicz 2021-04-20 14:30:12 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1951597]
Comment 7 Rohit Keshri 2021-05-16 17:44:12 UTC 
External References:

https://www.openwall.com/lists/oss-security/2021/04/18/4
Comment 8 Rohit Keshri 2021-05-17 11:11:24 UTC 
Mitigation:

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.   This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.

For the Red Hat Enterprise Linux 7 the eBPF for unprivileged users is always disabled.
For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:

# cat /proc/sys/kernel/unprivileged_bpf_disabled

The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.

A kernel update will be required to mitigate the flaw for the root or users with CAP_SYS_ADMIN capabilities.
Comment 12 errata-xmlrpc 2021-11-09 17:22:17 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4140 https://access.redhat.com/errata/RHSA-2021:4140
Comment 13 errata-xmlrpc 2021-11-09 18:25:01 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4356 https://access.redhat.com/errata/RHSA-2021:4356
Comment 14 Product Security DevOps Team 2021-11-09 20:24:25 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-29155
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