From 28a99e95f55c61855983d36a88c05c178d966bb7 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon, 18 Jul 2022 13:41:37 +0200
Subject: [PATCH 1/6] x86/amd: Use IBPB for firmware calls
On AMD IBRS does not prevent Retbleed; as such use IBPB before a
firmware call to flush the branch history state.
And because in order to do an EFI call, the kernel maps a whole lot of
the kernel page table into the EFI page table, do an IBPB just in case
in order to prevent the scenario of poisoning the BTB and causing an EFI
call using the unprotected RET there.
[ bp: Massage. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220715194550.793957-1-cascardo@canonical.com
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/nospec-branch.h | 2 ++
arch/x86/kernel/cpu/bugs.c | 11 ++++++++++-
3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 00f5227c84598..a77b915d36a8e 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -302,6 +302,7 @@
#define X86_FEATURE_RETPOLINE_LFENCE (11*32+13) /* "" Use LFENCE for Spectre variant 2 */
#define X86_FEATURE_RETHUNK (11*32+14) /* "" Use REturn THUNK */
#define X86_FEATURE_UNRET (11*32+15) /* "" AMD BTB untrain return */
+#define X86_FEATURE_USE_IBPB_FW (11*32+16) /* "" Use IBPB during runtime firmware calls */
/* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
#define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 10a3bfc1eb230..38a3e86e665ef 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -297,6 +297,8 @@ do { \
alternative_msr_write(MSR_IA32_SPEC_CTRL, \
spec_ctrl_current() | SPEC_CTRL_IBRS, \
X86_FEATURE_USE_IBRS_FW); \
+ alternative_msr_write(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, \
+ X86_FEATURE_USE_IBPB_FW); \
} while (0)
#define firmware_restrict_branch_speculation_end() \
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index aa34f908c39ff..78c9082242a9b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1516,7 +1516,16 @@ static void __init spectre_v2_select_mitigation(void)
* the CPU supports Enhanced IBRS, kernel might un-intentionally not
* enable IBRS around firmware calls.
*/
- if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) {
+ if (boot_cpu_has_bug(X86_BUG_RETBLEED) &&
+ (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
+ boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) {
+
+ if (retbleed_cmd != RETBLEED_CMD_IBPB) {
+ setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW);
+ pr_info("Enabling Speculation Barrier for firmware calls\n");
+ }
+
+ } else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) {
setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
pr_info("Enabling Restricted Speculation for firmware calls\n");
}
From 908fc4c2abdb1835f303cf6827e66676568943e7 Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Tue, 19 Jul 2022 12:12:52 -0500
Subject: [PATCH 2/6] virt: sev-guest: Pass the appropriate argument type to
iounmap()
Fix a sparse warning in sev_guest_probe() where the wrong argument type is
provided to iounmap().
Fixes: fce96cf04430 ("virt: Add SEV-SNP guest driver")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/202207150617.jqwQ0Rpz-lkp@intel.com
---
drivers/virt/coco/sev-guest/sev-guest.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 90ce16b6e05f9..f422f9c58ba79 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -632,16 +632,19 @@ static int __init sev_guest_probe(struct platform_device *pdev)
struct device *dev = &pdev->dev;
struct snp_guest_dev *snp_dev;
struct miscdevice *misc;
+ void __iomem *mapping;
int ret;
if (!dev->platform_data)
return -ENODEV;
data = (struct sev_guest_platform_data *)dev->platform_data;
- layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
- if (!layout)
+ mapping = ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
+ if (!mapping)
return -ENODEV;
+ layout = (__force void *)mapping;
+
ret = -ENOMEM;
snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
if (!snp_dev)
@@ -706,7 +709,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
e_free_request:
free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
e_unmap:
- iounmap(layout);
+ iounmap(mapping);
return ret;
}
From 65cdf0d623bedf0e069bb64ed52e8bb20105e2ba Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 13 Jul 2022 14:38:19 -0700
Subject: [PATCH 3/6] x86/alternative: Report missing return thunk details
Debugging missing return thunks is easier if we can see where they're
happening.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/Ys66hwtFcGbYmoiZ@hirez.programming.kicks-ass.net/
---
arch/x86/kernel/alternative.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index d6858533e6e59..62f6b8b7c4a52 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -555,7 +555,9 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
dest = addr + insn.length + insn.immediate.value;
if (__static_call_fixup(addr, op, dest) ||
- WARN_ON_ONCE(dest != &__x86_return_thunk))
+ WARN_ONCE(dest != &__x86_return_thunk,
+ "missing return thunk: %pS-%pS: %*ph",
+ addr, dest, 5, addr))
continue;
DPRINTK("return thunk at: %pS (%px) len: %d to: %pS",
From eb23b5ef9131e6d65011de349a4d25ef1b3d4314 Mon Sep 17 00:00:00 2001
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Thu, 14 Jul 2022 16:15:35 -0700
Subject: [PATCH 4/6] x86/bugs: Warn when "ibrs" mitigation is selected on
Enhanced IBRS parts
IBRS mitigation for spectre_v2 forces write to MSR_IA32_SPEC_CTRL at
every kernel entry/exit. On Enhanced IBRS parts setting
MSR_IA32_SPEC_CTRL[IBRS] only once at boot is sufficient. MSR writes at
every kernel entry/exit incur unnecessary performance loss.
When Enhanced IBRS feature is present, print a warning about this
unnecessary performance loss.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/2a5eaf54583c2bfe0edc4fea64006656256cca17.1657814857.git.pawan.kumar.gupta@linux.intel.com
---
arch/x86/kernel/cpu/bugs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 78c9082242a9b..6454bc767f0fd 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -975,6 +975,7 @@ static inline const char *spectre_v2_module_string(void) { return ""; }
#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
+#define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n"
#ifdef CONFIG_BPF_SYSCALL
void unpriv_ebpf_notify(int new_state)
@@ -1415,6 +1416,8 @@ static void __init spectre_v2_select_mitigation(void)
case SPECTRE_V2_IBRS:
setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS);
+ if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED))
+ pr_warn(SPECTRE_V2_IBRS_PERF_MSG);
break;
case SPECTRE_V2_LFENCE:
From efc72a665a61fd48c462f5248a9e3dc991398ddd Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: Mon, 18 Jul 2022 07:50:25 -0700
Subject: [PATCH 5/6] lkdtm: Disable return thunks in rodata.c
The following warning was seen:
WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:557 apply_returns (arch/x86/kernel/alternative.c:557 (discriminator 1))
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.19.0-rc4-00008-gee88d363d156 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-4 04/01/2014
RIP: 0010:apply_returns (arch/x86/kernel/alternative.c:557 (discriminator 1))
Code: ff ff 74 cb 48 83 c5 04 49 39 ee 0f 87 81 fe ff ff e9 22 ff ff ff 0f 0b 48 83 c5 04 49 39 ee 0f 87 6d fe ff ff e9 0e ff ff ff <0f> 0b 48 83 c5 04 49 39 ee 0f 87 59 fe ff ff e9 fa fe ff ff 48 89
The warning happened when apply_returns() failed to convert "JMP
__x86_return_thunk" to RET. It was instead a JMP to nowhere, due to the
thunk relocation not getting resolved.
That rodata.o code is objcopy'd to .rodata, and later memcpy'd, so
relocations don't work (and are apparently silently ignored).
LKDTM is only used for testing, so the naked RET should be fine. So
just disable return thunks for that file.
While at it, disable objtool and KCSAN for the file.
Fixes: 0b53c374b9ef ("x86/retpoline: Use -mfunction-return")
Reported-by: kernel test robot <oliver.sang@intel.com>
Debugged-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/Ys58BxHxoDZ7rfpr@xsang-OptiPlex-9020/
---
arch/x86/Makefile | 1 +
drivers/misc/lkdtm/Makefile | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1f40dad30d508..7854685c5f25b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -27,6 +27,7 @@ RETHUNK_CFLAGS := -mfunction-return=thunk-extern
RETPOLINE_CFLAGS += $(RETHUNK_CFLAGS)
endif
+export RETHUNK_CFLAGS
export RETPOLINE_CFLAGS
export RETPOLINE_VDSO_CFLAGS
diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
index 2e0aa74ac1850..95ef971b5e1cb 100644
--- a/drivers/misc/lkdtm/Makefile
+++ b/drivers/misc/lkdtm/Makefile
@@ -13,10 +13,13 @@ lkdtm-$(CONFIG_LKDTM) += cfi.o
lkdtm-$(CONFIG_LKDTM) += fortify.o
lkdtm-$(CONFIG_PPC_64S_HASH_MMU) += powerpc.o
-KASAN_SANITIZE_rodata.o := n
KASAN_SANITIZE_stackleak.o := n
-KCOV_INSTRUMENT_rodata.o := n
-CFLAGS_REMOVE_rodata.o += $(CC_FLAGS_LTO)
+
+KASAN_SANITIZE_rodata.o := n
+KCSAN_SANITIZE_rodata.o := n
+KCOV_INSTRUMENT_rodata.o := n
+OBJECT_FILES_NON_STANDARD_rodata.o := y
+CFLAGS_REMOVE_rodata.o += $(CC_FLAGS_LTO) $(RETHUNK_CFLAGS)
OBJCOPYFLAGS :=
OBJCOPYFLAGS_rodata_objcopy.o := \
From b648ab487f31bc4c38941bc770ea97fe394304bb Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben@decadent.org.uk>
Date: Sat, 23 Jul 2022 17:22:47 +0200
Subject: [PATCH 6/6] x86/speculation: Make all RETbleed mitigations 64-bit
only
The mitigations for RETBleed are currently ineffective on x86_32 since
entry_32.S does not use the required macros. However, for an x86_32
target, the kconfig symbols for them are still enabled by default and
/sys/devices/system/cpu/vulnerabilities/retbleed will wrongly report
that mitigations are in place.
Make all of these symbols depend on X86_64, and only enable RETHUNK by
default on X86_64.
Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/YtwSR3NNsWp1ohfV@decadent.org.uk
---
arch/x86/Kconfig | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e58798f636d47..1670a3fed263b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2473,7 +2473,7 @@ config RETHUNK
bool "Enable return-thunks"
depends on RETPOLINE && CC_HAS_RETURN_THUNK
select OBJTOOL if HAVE_OBJTOOL
- default y
+ default y if X86_64
help
Compile the kernel with the return-thunks compiler option to guard
against kernel-to-user data leaks by avoiding return speculation.
@@ -2482,21 +2482,21 @@ config RETHUNK
config CPU_UNRET_ENTRY
bool "Enable UNRET on kernel entry"
- depends on CPU_SUP_AMD && RETHUNK
+ depends on CPU_SUP_AMD && RETHUNK && X86_64
default y
help
Compile the kernel with support for the retbleed=unret mitigation.
config CPU_IBPB_ENTRY
bool "Enable IBPB on kernel entry"
- depends on CPU_SUP_AMD
+ depends on CPU_SUP_AMD && X86_64
default y
help
Compile the kernel with support for the retbleed=ibpb mitigation.
config CPU_IBRS_ENTRY
bool "Enable IBRS on kernel entry"
- depends on CPU_SUP_INTEL
+ depends on CPU_SUP_INTEL && X86_64
default y
help
Compile the kernel with support for the spectre_v2=ibrs mitigation.