From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Borislav Petkov <bp@suse.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH 5.16 03/37] Documentation/hw-vuln: Update spectre doc
Date: Wed, 9 Mar 2022 17:00:04 +0100 [thread overview]
Message-ID: <20220309155859.188409810@linuxfoundation.org> (raw)
In-Reply-To: <20220309155859.086952723@linuxfoundation.org>
From: Peter Zijlstra <peterz@infradead.org>
commit 5ad3eb1132453b9795ce5fd4572b1c18b292cca9 upstream.
Update the doc with the new fun.
[ bp: Massage commit message. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 44 ++++++++++++++++--------
Documentation/admin-guide/kernel-parameters.txt | 8 +++-
2 files changed, 36 insertions(+), 16 deletions(-)
--- a/Documentation/admin-guide/hw-vuln/spectre.rst
+++ b/Documentation/admin-guide/hw-vuln/spectre.rst
@@ -131,6 +131,19 @@ steer its indirect branch speculations t
speculative execution's side effects left in level 1 cache to infer the
victim's data.
+Yet another variant 2 attack vector is for the attacker to poison the
+Branch History Buffer (BHB) to speculatively steer an indirect branch
+to a specific Branch Target Buffer (BTB) entry, even if the entry isn't
+associated with the source address of the indirect branch. Specifically,
+the BHB might be shared across privilege levels even in the presence of
+Enhanced IBRS.
+
+Currently the only known real-world BHB attack vector is via
+unprivileged eBPF. Therefore, it's highly recommended to not enable
+unprivileged eBPF, especially when eIBRS is used (without retpolines).
+For a full mitigation against BHB attacks, it's recommended to use
+retpolines (or eIBRS combined with retpolines).
+
Attack scenarios
----------------
@@ -364,13 +377,15 @@ The possible values in this file are:
- Kernel status:
- ==================================== =================================
- 'Not affected' The processor is not vulnerable
- 'Vulnerable' Vulnerable, no mitigation
- 'Mitigation: Full generic retpoline' Software-focused mitigation
- 'Mitigation: Full AMD retpoline' AMD-specific software mitigation
- 'Mitigation: Enhanced IBRS' Hardware-focused mitigation
- ==================================== =================================
+ ======================================== =================================
+ 'Not affected' The processor is not vulnerable
+ 'Mitigation: None' Vulnerable, no mitigation
+ 'Mitigation: Retpolines' Use Retpoline thunks
+ 'Mitigation: LFENCE' Use LFENCE instructions
+ 'Mitigation: Enhanced IBRS' Hardware-focused mitigation
+ 'Mitigation: Enhanced IBRS + Retpolines' Hardware-focused + Retpolines
+ 'Mitigation: Enhanced IBRS + LFENCE' Hardware-focused + LFENCE
+ ======================================== =================================
- Firmware status: Show if Indirect Branch Restricted Speculation (IBRS) is
used to protect against Spectre variant 2 attacks when calling firmware (x86 only).
@@ -583,12 +598,13 @@ kernel command line.
Specific mitigations can also be selected manually:
- retpoline
- replace indirect branches
- retpoline,generic
- google's original retpoline
- retpoline,amd
- AMD-specific minimal thunk
+ retpoline auto pick between generic,lfence
+ retpoline,generic Retpolines
+ retpoline,lfence LFENCE; indirect branch
+ retpoline,amd alias for retpoline,lfence
+ eibrs enhanced IBRS
+ eibrs,retpoline enhanced IBRS + Retpolines
+ eibrs,lfence enhanced IBRS + LFENCE
Not specifying this option is equivalent to
spectre_v2=auto.
@@ -599,7 +615,7 @@ kernel command line.
spectre_v2=off. Spectre variant 1 mitigations
cannot be disabled.
-For spectre_v2_user see :doc:`/admin-guide/kernel-parameters`.
+For spectre_v2_user see Documentation/admin-guide/kernel-parameters.txt
Mitigation selection guide
--------------------------
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5303,8 +5303,12 @@
Specific mitigations can also be selected manually:
retpoline - replace indirect branches
- retpoline,generic - google's original retpoline
- retpoline,amd - AMD-specific minimal thunk
+ retpoline,generic - Retpolines
+ retpoline,lfence - LFENCE; indirect branch
+ retpoline,amd - alias for retpoline,lfence
+ eibrs - enhanced IBRS
+ eibrs,retpoline - enhanced IBRS + Retpolines
+ eibrs,lfence - enhanced IBRS + LFENCE
Not specifying this option is equivalent to
spectre_v2=auto.
next prev parent reply other threads:[~2022-03-09 16:22 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 16:00 [PATCH 5.16 00/37] 5.16.14-rc1 review Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 01/37] x86/speculation: Rename RETPOLINE_AMD to RETPOLINE_LFENCE Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 02/37] x86/speculation: Add eIBRS + Retpoline options Greg Kroah-Hartman
2022-03-09 16:00 ` Greg Kroah-Hartman [this message]
2022-03-09 16:00 ` [PATCH 5.16 04/37] x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 05/37] x86/speculation: Use generic retpoline by default on AMD Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 06/37] x86/speculation: Update link to AMD speculation whitepaper Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 07/37] x86/speculation: Warn about Spectre v2 LFENCE mitigation Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 08/37] x86/speculation: Warn about eIBRS + LFENCE + Unprivileged eBPF + SMT Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 09/37] ARM: report Spectre v2 status through sysfs Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 10/37] ARM: early traps initialisation Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 11/37] ARM: use LOADADDR() to get load address of sections Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 12/37] ARM: Spectre-BHB workaround Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 13/37] ARM: include unprivileged BPF status in Spectre V2 reporting Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 14/37] arm64: add ID_AA64ISAR2_EL1 sys register Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 15/37] arm64: cpufeature: add HWCAP for FEAT_AFP Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 16/37] arm64: cpufeature: add HWCAP for FEAT_RPRES Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 17/37] arm64: entry.S: Add ventry overflow sanity checks Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 18/37] arm64: spectre: Rename spectre_v4_patch_fw_mitigation_conduit Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 19/37] KVM: arm64: Allow indirect vectors to be used without SPECTRE_V3A Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 20/37] arm64: entry: Make the trampoline cleanup optional Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 21/37] arm64: entry: Free up another register on kptis tramp_exit path Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 22/37] arm64: entry: Move the trampoline data page before the text page Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 23/37] arm64: entry: Allow tramp_alias to access symbols after the 4K boundary Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 24/37] arm64: entry: Dont assume tramp_vectors is the start of the vectors Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 25/37] arm64: entry: Move trampoline macros out of ifdefd section Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 26/37] arm64: entry: Make the kpti trampolines kpti sequence optional Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 27/37] arm64: entry: Allow the trampoline text to occupy multiple pages Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 28/37] arm64: entry: Add non-kpti __bp_harden_el1_vectors for mitigations Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 29/37] arm64: entry: Add vectors that have the bhb mitigation sequences Greg Kroah-Hartman
2022-03-10 23:27 ` Pavel Machek
2022-03-11 8:15 ` Greg Kroah-Hartman
2022-03-11 8:39 ` Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 30/37] arm64: entry: Add macro for reading symbol addresses from the trampoline Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 31/37] arm64: Add percpu vectors for EL1 Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 32/37] arm64: proton-pack: Report Spectre-BHB vulnerabilities as part of Spectre-v2 Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 33/37] arm64: Mitigate spectre style branch history side channels Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 34/37] KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 35/37] arm64: Use the clearbhb instruction in mitigations Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 36/37] arm64: proton-pack: Include unprivileged eBPF status in Spectre v2 mitigation reporting Greg Kroah-Hartman
2022-03-09 16:00 ` [PATCH 5.16 37/37] ARM: fix build error when BPF_SYSCALL is disabled Greg Kroah-Hartman
2022-03-09 19:05 ` [PATCH 5.16 00/37] 5.16.14-rc1 review Guenter Roeck
2022-03-09 20:01 ` Greg Kroah-Hartman
2022-03-09 21:17 ` Greg Kroah-Hartman
2022-03-09 20:23 ` Shuah Khan
2022-03-09 21:17 ` Daniel Díaz
2022-03-09 21:19 ` Daniel Díaz
2022-03-09 21:49 ` Fox Chen
2022-03-10 10:50 ` Bagas Sanjaya
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