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authorLinus Torvalds <torvalds@linux-foundation.org>2023-08-12 08:34:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-08-12 08:34:20 -0700
commit272b86ba9d97518b3c14b97514b6544eef87e7a5 (patch)
tree038a5b84e3e61ff0470d53ef1f7be2447ab52f58 /Documentation
parentf8de32cc060ba3f63171aaa0e8764d22d8c37978 (diff)
parent3477144c878a52fc3938a529186e81ea030e7779 (diff)
downloadlwn-272b86ba9d97518b3c14b97514b6544eef87e7a5.tar.gz
lwn-272b86ba9d97518b3c14b97514b6544eef87e7a5.zip
Merge tag 'x86_bugs_for_v6.5_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 mitigation fixes from Borislav Petkov: "The first set of fallout fixes after the embargo madness. There will be another set next week too. - A first series of cleanups/unifications and documentation improvements to the SRSO and GDS mitigations code which got postponed to after the embargo date - Fix the SRSO aliasing addresses assertion so that the LLVM linker can parse it too" * tag 'x86_bugs_for_v6.5_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: driver core: cpu: Fix the fallback cpu_show_gds() name x86: Move gds_ucode_mitigated() declaration to header x86/speculation: Add cpu_show_gds() prototype driver core: cpu: Make cpu_show_not_affected() static x86/srso: Fix build breakage with the LLVM linker Documentation/srso: Document IBPB aspect and fix formatting driver core: cpu: Unify redundant silly stubs Documentation/hw-vuln: Unify filename specification in index
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/hw-vuln/index.rst14
-rw-r--r--Documentation/admin-guide/hw-vuln/srso.rst71
2 files changed, 51 insertions, 34 deletions
diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
index a7d37e124831..de99caabf65a 100644
--- a/Documentation/admin-guide/hw-vuln/index.rst
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -13,11 +13,11 @@ are configurable at compile, boot or run time.
l1tf
mds
tsx_async_abort
- multihit.rst
- special-register-buffer-data-sampling.rst
- core-scheduling.rst
- l1d_flush.rst
- processor_mmio_stale_data.rst
- cross-thread-rsb.rst
+ multihit
+ special-register-buffer-data-sampling
+ core-scheduling
+ l1d_flush
+ processor_mmio_stale_data
+ cross-thread-rsb
srso
- gather_data_sampling.rst
+ gather_data_sampling
diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index 32eb5e6db272..af59a9395662 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -42,42 +42,59 @@ The sysfs file showing SRSO mitigation status is:
The possible values in this file are:
- - 'Not affected' The processor is not vulnerable
+ * 'Not affected':
- - 'Vulnerable: no microcode' The processor is vulnerable, no
- microcode extending IBPB functionality
- to address the vulnerability has been
- applied.
+ The processor is not vulnerable
- - 'Mitigation: microcode' Extended IBPB functionality microcode
- patch has been applied. It does not
- address User->Kernel and Guest->Host
- transitions protection but it does
- address User->User and VM->VM attack
- vectors.
+ * 'Vulnerable: no microcode':
- (spec_rstack_overflow=microcode)
+ The processor is vulnerable, no microcode extending IBPB
+ functionality to address the vulnerability has been applied.
- - 'Mitigation: safe RET' Software-only mitigation. It complements
- the extended IBPB microcode patch
- functionality by addressing User->Kernel
- and Guest->Host transitions protection.
+ * 'Mitigation: microcode':
- Selected by default or by
- spec_rstack_overflow=safe-ret
+ Extended IBPB functionality microcode patch has been applied. It does
+ not address User->Kernel and Guest->Host transitions protection but it
+ does address User->User and VM->VM attack vectors.
- - 'Mitigation: IBPB' Similar protection as "safe RET" above
- but employs an IBPB barrier on privilege
- domain crossings (User->Kernel,
- Guest->Host).
+ Note that User->User mitigation is controlled by how the IBPB aspect in
+ the Spectre v2 mitigation is selected:
- (spec_rstack_overflow=ibpb)
+ * conditional IBPB:
+
+ where each process can select whether it needs an IBPB issued
+ around it PR_SPEC_DISABLE/_ENABLE etc, see :doc:`spectre`
+
+ * strict:
+
+ i.e., always on - by supplying spectre_v2_user=on on the kernel
+ command line
+
+ (spec_rstack_overflow=microcode)
+
+ * 'Mitigation: safe RET':
+
+ Software-only mitigation. It complements the extended IBPB microcode
+ patch functionality by addressing User->Kernel and Guest->Host
+ transitions protection.
+
+ Selected by default or by spec_rstack_overflow=safe-ret
+
+ * 'Mitigation: IBPB':
+
+ Similar protection as "safe RET" above but employs an IBPB barrier on
+ privilege domain crossings (User->Kernel, Guest->Host).
+
+ (spec_rstack_overflow=ibpb)
+
+ * 'Mitigation: IBPB on VMEXIT':
+
+ Mitigation addressing the cloud provider scenario - the Guest->Host
+ transitions only.
+
+ (spec_rstack_overflow=ibpb-vmexit)
- - 'Mitigation: IBPB on VMEXIT' Mitigation addressing the cloud provider
- scenario - the Guest->Host transitions
- only.
- (spec_rstack_overflow=ibpb-vmexit)
In order to exploit vulnerability, an attacker needs to: