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authorLinus Torvalds <torvalds@linux-foundation.org>2020-11-19 11:32:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-11-19 11:32:31 -0800
commitdda3f4252e6c8b833a2ef164afd3da9808d0f07c (patch)
tree9a294782b7d3d4fd3c48f16bf39d57b34be44ad1 /Documentation
parent3494d58865ad4a47611dbb427b214cc5227fa5eb (diff)
parentda631f7fd623b6c180c8d93a93040d1e0d61291f (diff)
Merge tag 'powerpc-cve-2020-4788' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fixes from Michael Ellerman: "Fixes for CVE-2020-4788. From Daniel's cover letter: IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked. However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack. This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch series flushes the L1 cache on kernel entry (patch 2) and after the kernel performs any user accesses (patch 3). It also adds a self-test and performs some related cleanups" * tag 'powerpc-cve-2020-4788' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: powerpc/64s: rename pnv|pseries_setup_rfi_flush to _setup_security_mitigations selftests/powerpc: refactor entry and rfi_flush tests selftests/powerpc: entry flush test powerpc: Only include kup-radix.h for 64-bit Book3S powerpc/64s: flush L1D after user accesses powerpc/64s: flush L1D on kernel entry selftests/powerpc: rfi_flush: disable entry flush if present
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..44fde25bb221 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2858,6 +2858,8 @@
mds=off [X86]
tsx_async_abort=off [X86]
kvm.nx_huge_pages=off [X86]
+ no_entry_flush [PPC]
+ no_uaccess_flush [PPC]
Exceptions:
This does not have any effect on
@@ -3186,6 +3188,8 @@
noefi Disable EFI runtime services support.
+ no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
+
noexec [IA-64]
noexec [X86]
@@ -3235,6 +3239,9 @@
nospec_store_bypass_disable
[HW] Disable all mitigations for the Speculative Store Bypass vulnerability
+ no_uaccess_flush
+ [PPC] Don't flush the L1-D cache after accessing user data.
+
noxsave [BUGS=X86] Disables x86 extended register state save
and restore using xsave. The kernel will fallback to
enabling legacy floating-point and sse state.