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authorLinus Torvalds <torvalds@linux-foundation.org>2022-07-24 09:40:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-07-24 09:40:17 -0700
commit05017fed92de32c167bbd21a5ee9ad0e489e19d4 (patch)
tree8a6dc58200f290dabf1a131811f83296ef49f378 /arch
parent714b82c18ba0d2e76e9c3fd7785ff5a060f5980b (diff)
parentb648ab487f31bc4c38941bc770ea97fe394304bb (diff)
Merge tag 'x86_urgent_for_v5.19_rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov: "A couple more retbleed fallout fixes. It looks like their urgency is decreasing so it seems like we've managed to catch whatever snafus the limited -rc testing has exposed. Maybe we're getting ready... :) - Make retbleed mitigations 64-bit only (32-bit will need a bit more work if even needed, at all). - Prevent return thunks patching of the LKDTM modules as it is not needed there - Avoid writing the SPEC_CTRL MSR on every kernel entry on eIBRS parts - Enhance error output of apply_returns() when it fails to patch a return thunk - A sparse fix to the sev-guest module - Protect EFI fw calls by issuing an IBPB on AMD" * tag 'x86_urgent_for_v5.19_rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/speculation: Make all RETbleed mitigations 64-bit only lkdtm: Disable return thunks in rodata.c x86/bugs: Warn when "ibrs" mitigation is selected on Enhanced IBRS parts x86/alternative: Report missing return thunk details virt: sev-guest: Pass the appropriate argument type to iounmap() x86/amd: Use IBPB for firmware calls
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/Kconfig8
-rw-r--r--arch/x86/Makefile1
-rw-r--r--arch/x86/include/asm/cpufeatures.h1
-rw-r--r--arch/x86/include/asm/nospec-branch.h2
-rw-r--r--arch/x86/kernel/alternative.c4
-rw-r--r--arch/x86/kernel/cpu/bugs.c14
6 files changed, 24 insertions, 6 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7fff10e15969..52a7f91527fe 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2474,7 +2474,7 @@ 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.
@@ -2483,21 +2483,21 @@ 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.
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1f40dad30d50..7854685c5f25 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/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 00f5227c8459..a77b915d36a8 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 10a3bfc1eb23..38a3e86e665e 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/alternative.c b/arch/x86/kernel/alternative.c
index d6858533e6e5..62f6b8b7c4a5 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",
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index aa34f908c39f..6454bc767f0f 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:
@@ -1516,7 +1519,16 @@ 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");
}

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