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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-19 22:32:31 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-19 22:32:31 +0300 |
| commit | dda3f4252e6c8b833a2ef164afd3da9808d0f07c (patch) | |
| tree | 9a294782b7d3d4fd3c48f16bf39d57b34be44ad1 /Documentation | |
| parent | 3494d58865ad4a47611dbb427b214cc5227fa5eb (diff) | |
| parent | da631f7fd623b6c180c8d93a93040d1e0d61291f (diff) | |
| download | linux-dda3f4252e6c8b833a2ef164afd3da9808d0f07c.tar.xz | |
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.txt | 7 |
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. |