From: Rob Herring <robh@kernel.org>
Date: Thu, 21 Sep 2023 14:41:52 -0500
Subject: arm64: errata: Add Cortex-A520 speculative unprivileged load
workaround
Git-commit: 471470bc7052d28ce125901877dd10e4c048e513
Patch-mainline: v6.6-rc5
References: bsc#1219443, bsc#1220887, CVE-2023-52481
Implement the workaround for ARM Cortex-A520 erratum 2966298. On an
affected Cortex-A520 core, a speculatively executed unprivileged load
might leak data from a privileged load via a cache side channel. The
issue only exists for loads within a translation regime with the same
translation (e.g. same ASID and VMID). Therefore, the issue only affects
the return to EL0.
The workaround is to execute a TLBI before returning to EL0 after all
loads of privileged data. A non-shareable TLBI to any address is
sufficient.
The workaround isn't necessary if page table isolation (KPTI) is
enabled, but for simplicity it will be. Page table isolation should
normally be disabled for Cortex-A520 as it supports the CSV3 feature
and the E0PD feature (used when KASLR is enabled).
Cc: stable@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230921194156.1050055-2-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Ivan T. Ivanov <iivanov@suse.de>
---
arch/arm64/Kconfig | 13 +++++++++++++
arch/arm64/kernel/cpu_errata.c | 8 ++++++++
arch/arm64/kernel/entry.S | 4 ++++
arch/arm64/tools/cpucaps | 1 +
4 files changed, 26 insertions(+)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -869,6 +869,19 @@ config ARM64_ERRATUM_2457168
If unsure, say Y.
+config ARM64_ERRATUM_2966298
+ bool "Cortex-A520: 2966298: workaround for speculatively executed unprivileged load"
+ default y
+ help
+ This option adds the workaround for ARM Cortex-A520 erratum 2966298.
+
+ On an affected Cortex-A520 core, a speculatively executed unprivileged
+ load might leak data from a privileged level via a cache side channel.
+
+ Work around this problem by executing a TLBI before returning to EL0.
+
+ If unsure, say Y.
+
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -661,6 +661,14 @@ const struct arm64_cpu_capabilities arm6
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
},
#endif
+#ifdef CONFIG_ARM64_ERRATUM_2966298
+ {
+ .desc = "ARM erratum 2966298",
+ .capability = ARM64_WORKAROUND_2966298,
+ /* Cortex-A520 r0p0 - r0p1 */
+ ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A520, 0, 0, 1),
+ },
+#endif
#ifdef CONFIG_AMPERE_ERRATUM_AC03_CPU_38
{
.desc = "AmpereOne erratum AC03_CPU_38",
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -414,6 +414,10 @@ alternative_else_nop_endif
ldp x28, x29, [sp, #16 * 14]
.if \el == 0
+alternative_if ARM64_WORKAROUND_2966298
+ tlbi vale1, xzr
+ dsb nsh
+alternative_else_nop_endif
alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0
ldr lr, [sp, #S_LR]
add sp, sp, #PT_REGS_SIZE // restore sp
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -55,6 +55,7 @@ WORKAROUND_1463225
WORKAROUND_1508412
WORKAROUND_1542419
WORKAROUND_1742098
+WORKAROUND_2966298
WORKAROUND_AMPERE_AC03_CPU_38
WORKAROUND_TRBE_OVERWRITE_FILL_MODE
WORKAROUND_TSB_FLUSH_FAILURE