Subject: CVE-2021-46908: bpf: Use correct permission flag for mixed signed bounds arithmetic

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

bpf: Use correct permission flag for mixed signed bounds arithmetic

We forbid adding unknown scalars with mixed signed bounds due to the
spectre v1 masking mitigation. Hence this also needs bypass_spec_v1
flag instead of allow_ptr_leaks.

The Linux kernel CVE team has assigned CVE-2021-46908 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.8 with commit 2c78ee898d8f and fixed in 5.10.32 with commit 4f3ff11204ea
	Issue introduced in 5.8 with commit 2c78ee898d8f and fixed in 5.11.16 with commit 4ccdc6c6cae3
	Issue introduced in 5.8 with commit 2c78ee898d8f and fixed in 5.12 with commit 960114839252

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-46908
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/verifier.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4f3ff11204eac0ee23acf64deecb3bad7b0db0c6
	https://git.kernel.org/stable/c/4ccdc6c6cae38b91c871293fb0ed8c6845a61b51
	https://git.kernel.org/stable/c/9601148392520e2e134936e76788fc2a6371e7be