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>,
Frank van der Linden <fllinden@amazon.com>
Subject: [PATCH 5.15 05/58] Documentation/hw-vuln: Update spectre doc
Date: Thu, 10 Mar 2022 15:18:54 +0100 [thread overview]
Message-ID: <20220310140813.141110266@linuxfoundation.org> (raw)
In-Reply-To: <20220310140812.983088611@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>
[fllinden@amazon.com: backported to 5.15]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/admin-guide/hw-vuln/spectre.rst | 42 ++++++++++++++++--------
Documentation/admin-guide/kernel-parameters.txt | 8 +++-
2 files changed, 35 insertions(+), 15 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).
@@ -584,12 +599,13 @@ 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.
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5267,8 +5267,12 @@
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:[~2022-03-10 14:34 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 14:18 [PATCH 5.15 00/58] 5.15.28-rc2 review Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 01/58] slip: fix macro redefine warning Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 02/58] x86,bugs: Unconditionally allow spectre_v2=retpoline,amd Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 03/58] x86/speculation: Rename RETPOLINE_AMD to RETPOLINE_LFENCE Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 04/58] x86/speculation: Add eIBRS + Retpoline options Greg Kroah-Hartman
2022-03-10 14:18 ` Greg Kroah-Hartman [this message]
2022-03-10 14:18 ` [PATCH 5.15 06/58] x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 07/58] x86/speculation: Use generic retpoline by default on AMD Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 08/58] x86/speculation: Update link to AMD speculation whitepaper Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 09/58] x86/speculation: Warn about Spectre v2 LFENCE mitigation Greg Kroah-Hartman
2022-03-10 14:18 ` [PATCH 5.15 10/58] x86/speculation: Warn about eIBRS + LFENCE + Unprivileged eBPF + SMT Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 11/58] ARM: report Spectre v2 status through sysfs Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 12/58] ARM: early traps initialisation Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 13/58] ARM: use LOADADDR() to get load address of sections Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 14/58] ARM: Spectre-BHB workaround Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 15/58] ARM: include unprivileged BPF status in Spectre V2 reporting Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 16/58] arm64: Add Neoverse-N2, Cortex-A710 CPU part definition Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 17/58] arm64: Add HWCAP for self-synchronising virtual counter Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 18/58] arm64: Add Cortex-X2 CPU part definition Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 19/58] arm64: add ID_AA64ISAR2_EL1 sys register Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 20/58] arm64: cpufeature: add HWCAP for FEAT_AFP Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 21/58] arm64: cpufeature: add HWCAP for FEAT_RPRES Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 22/58] arm64: entry.S: Add ventry overflow sanity checks Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 23/58] arm64: spectre: Rename spectre_v4_patch_fw_mitigation_conduit Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 24/58] KVM: arm64: Allow indirect vectors to be used without SPECTRE_V3A Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 25/58] arm64: entry: Make the trampoline cleanup optional Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 26/58] arm64: entry: Free up another register on kptis tramp_exit path Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 27/58] arm64: entry: Move the trampoline data page before the text page Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 28/58] arm64: entry: Allow tramp_alias to access symbols after the 4K boundary Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 29/58] arm64: entry: Dont assume tramp_vectors is the start of the vectors Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 30/58] arm64: entry: Move trampoline macros out of ifdefd section Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 31/58] arm64: entry: Make the kpti trampolines kpti sequence optional Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 32/58] arm64: entry: Allow the trampoline text to occupy multiple pages Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 33/58] arm64: entry: Add non-kpti __bp_harden_el1_vectors for mitigations Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 34/58] arm64: entry: Add vectors that have the bhb mitigation sequences Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 35/58] arm64: entry: Add macro for reading symbol addresses from the trampoline Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 36/58] arm64: Add percpu vectors for EL1 Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 37/58] arm64: proton-pack: Report Spectre-BHB vulnerabilities as part of Spectre-v2 Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 38/58] arm64: Mitigate spectre style branch history side channels Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 39/58] KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 40/58] arm64: Use the clearbhb instruction in mitigations Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 41/58] arm64: proton-pack: Include unprivileged eBPF status in Spectre v2 mitigation reporting Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 42/58] ARM: fix build error when BPF_SYSCALL is disabled Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 43/58] ARM: fix co-processor register typo Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 44/58] ARM: Do not use NOCROSSREFS directive with ld.lld Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 45/58] arm64: Do not include __READ_ONCE() block in assembly files Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 46/58] ARM: fix build warning in proc-v7-bugs.c Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 47/58] xen/xenbus: dont let xenbus_grant_ring() remove grants in error case Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 48/58] xen/grant-table: add gnttab_try_end_foreign_access() Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 49/58] xen/blkfront: dont use gnttab_query_foreign_access() for mapped status Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 50/58] xen/netfront: " Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 51/58] xen/scsifront: " Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 52/58] xen/gntalloc: dont use gnttab_query_foreign_access() Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 53/58] xen: remove gnttab_query_foreign_access() Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 54/58] xen/9p: use alloc/free_pages_exact() Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 55/58] xen/pvcalls: " Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 56/58] xen/gnttab: fix gnttab_end_foreign_access() without page specified Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 57/58] xen/netfront: react properly to failing gnttab_end_foreign_access_ref() Greg Kroah-Hartman
2022-03-10 14:19 ` [PATCH 5.15 58/58] Revert "ACPI: PM: s2idle: Cancel wakeup before dispatching EC GPE" Greg Kroah-Hartman
2022-03-10 18:48 ` [PATCH 5.15 00/58] 5.15.28-rc2 review Jon Hunter
2022-03-10 19:04 ` Fox Chen
2022-03-10 19:32 ` Shuah Khan
2022-03-10 22:12 ` Florian Fainelli
2022-03-11 1:03 ` Guenter Roeck
2022-03-11 7:34 ` Ron Economos
2022-03-11 8:27 ` Bagas Sanjaya
2022-03-11 10:08 ` Sudip Mukherjee
2022-03-11 10:26 ` Anders Roxell
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