diff options
Diffstat (limited to '0048-x86-spinlock-introduce-support-for-blocking-speculat.patch')
| -rw-r--r-- | 0048-x86-spinlock-introduce-support-for-blocking-speculat.patch | 331 |
1 files changed, 331 insertions, 0 deletions
diff --git a/0048-x86-spinlock-introduce-support-for-blocking-speculat.patch b/0048-x86-spinlock-introduce-support-for-blocking-speculat.patch new file mode 100644 index 0000000..ecf0830 --- /dev/null +++ b/0048-x86-spinlock-introduce-support-for-blocking-speculat.patch @@ -0,0 +1,331 @@ +From 9d2f136328aab5537b7180a1b23e171893ebe455 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com> +Date: Tue, 13 Feb 2024 13:08:05 +0100 +Subject: [PATCH 48/67] x86/spinlock: introduce support for blocking + speculation into critical regions +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Introduce a new Kconfig option to block speculation into lock protected +critical regions. The Kconfig option is enabled by default, but the mitigation +won't be engaged unless it's explicitly enabled in the command line using +`spec-ctrl=lock-harden`. + +Convert the spinlock acquire macros into always-inline functions, and introduce +a speculation barrier after the lock has been taken. Note the speculation +barrier is not placed inside the implementation of the spin lock functions, as +to prevent speculation from falling through the call to the lock functions +resulting in the barrier also being skipped. + +trylock variants are protected using a construct akin to the existing +evaluate_nospec(). + +This patch only implements the speculation barrier for x86. + +Note spin locks are the only locking primitive taken care in this change, +further locking primitives will be adjusted by separate changes. + +This is part of XSA-453 / CVE-2024-2193 + +Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> +Reviewed-by: Jan Beulich <jbeulich@suse.com> +(cherry picked from commit 7ef0084418e188d05f338c3e028fbbe8b6924afa) +--- + docs/misc/xen-command-line.pandoc | 7 ++++- + xen/arch/x86/include/asm/cpufeatures.h | 2 +- + xen/arch/x86/include/asm/nospec.h | 26 ++++++++++++++++++ + xen/arch/x86/spec_ctrl.c | 26 +++++++++++++++--- + xen/common/Kconfig | 17 ++++++++++++ + xen/include/xen/nospec.h | 15 +++++++++++ + xen/include/xen/spinlock.h | 37 +++++++++++++++++++++----- + 7 files changed, 119 insertions(+), 11 deletions(-) + +diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc +index d909ec94fe..e1d56407dd 100644 +--- a/docs/misc/xen-command-line.pandoc ++++ b/docs/misc/xen-command-line.pandoc +@@ -2327,7 +2327,7 @@ By default SSBD will be mitigated at runtime (i.e `ssbd=runtime`). + > {msr-sc,rsb,verw,ibpb-entry}=<bool>|{pv,hvm}=<bool>, + > bti-thunk=retpoline|lfence|jmp, {ibrs,ibpb,ssbd,psfd, + > eager-fpu,l1d-flush,branch-harden,srb-lock, +-> unpriv-mmio,gds-mit,div-scrub}=<bool> ]` ++> unpriv-mmio,gds-mit,div-scrub,lock-harden}=<bool> ]` + + Controls for speculative execution sidechannel mitigations. By default, Xen + will pick the most appropriate mitigations based on compiled in support, +@@ -2454,6 +2454,11 @@ On all hardware, the `div-scrub=` option can be used to force or prevent Xen + from mitigating the DIV-leakage vulnerability. By default, Xen will mitigate + DIV-leakage on hardware believed to be vulnerable. + ++If Xen is compiled with `CONFIG_SPECULATIVE_HARDEN_LOCK`, the `lock-harden=` ++boolean can be used to force or prevent Xen from using speculation barriers to ++protect lock critical regions. This mitigation won't be engaged by default, ++and needs to be explicitly enabled on the command line. ++ + ### sync_console + > `= <boolean>` + +diff --git a/xen/arch/x86/include/asm/cpufeatures.h b/xen/arch/x86/include/asm/cpufeatures.h +index c3aad21c3b..7e8221fd85 100644 +--- a/xen/arch/x86/include/asm/cpufeatures.h ++++ b/xen/arch/x86/include/asm/cpufeatures.h +@@ -24,7 +24,7 @@ XEN_CPUFEATURE(APERFMPERF, X86_SYNTH( 8)) /* APERFMPERF */ + XEN_CPUFEATURE(MFENCE_RDTSC, X86_SYNTH( 9)) /* MFENCE synchronizes RDTSC */ + XEN_CPUFEATURE(XEN_SMEP, X86_SYNTH(10)) /* SMEP gets used by Xen itself */ + XEN_CPUFEATURE(XEN_SMAP, X86_SYNTH(11)) /* SMAP gets used by Xen itself */ +-/* Bit 12 unused. */ ++XEN_CPUFEATURE(SC_NO_LOCK_HARDEN, X86_SYNTH(12)) /* (Disable) Lock critical region hardening */ + XEN_CPUFEATURE(IND_THUNK_LFENCE, X86_SYNTH(13)) /* Use IND_THUNK_LFENCE */ + XEN_CPUFEATURE(IND_THUNK_JMP, X86_SYNTH(14)) /* Use IND_THUNK_JMP */ + XEN_CPUFEATURE(SC_NO_BRANCH_HARDEN, X86_SYNTH(15)) /* (Disable) Conditional branch hardening */ +diff --git a/xen/arch/x86/include/asm/nospec.h b/xen/arch/x86/include/asm/nospec.h +index 7150e76b87..0725839e19 100644 +--- a/xen/arch/x86/include/asm/nospec.h ++++ b/xen/arch/x86/include/asm/nospec.h +@@ -38,6 +38,32 @@ static always_inline void block_speculation(void) + barrier_nospec_true(); + } + ++static always_inline void arch_block_lock_speculation(void) ++{ ++ alternative("lfence", "", X86_FEATURE_SC_NO_LOCK_HARDEN); ++} ++ ++/* Allow to insert a read memory barrier into conditionals */ ++static always_inline bool barrier_lock_true(void) ++{ ++ alternative("lfence #nospec-true", "", X86_FEATURE_SC_NO_LOCK_HARDEN); ++ return true; ++} ++ ++static always_inline bool barrier_lock_false(void) ++{ ++ alternative("lfence #nospec-false", "", X86_FEATURE_SC_NO_LOCK_HARDEN); ++ return false; ++} ++ ++static always_inline bool arch_lock_evaluate_nospec(bool condition) ++{ ++ if ( condition ) ++ return barrier_lock_true(); ++ else ++ return barrier_lock_false(); ++} ++ + #endif /* _ASM_X86_NOSPEC_H */ + + /* +diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c +index 1ee81e2dfe..ac21af2c5c 100644 +--- a/xen/arch/x86/spec_ctrl.c ++++ b/xen/arch/x86/spec_ctrl.c +@@ -65,6 +65,7 @@ int8_t __read_mostly opt_eager_fpu = -1; + int8_t __read_mostly opt_l1d_flush = -1; + static bool __initdata opt_branch_harden = + IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_BRANCH); ++static bool __initdata opt_lock_harden; + + bool __initdata bsp_delay_spec_ctrl; + uint8_t __read_mostly default_xen_spec_ctrl; +@@ -133,6 +134,7 @@ static int __init cf_check parse_spec_ctrl(const char *s) + opt_ssbd = false; + opt_l1d_flush = 0; + opt_branch_harden = false; ++ opt_lock_harden = false; + opt_srb_lock = 0; + opt_unpriv_mmio = false; + opt_gds_mit = 0; +@@ -298,6 +300,16 @@ static int __init cf_check parse_spec_ctrl(const char *s) + rc = -EINVAL; + } + } ++ else if ( (val = parse_boolean("lock-harden", s, ss)) >= 0 ) ++ { ++ if ( IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_LOCK) ) ++ opt_lock_harden = val; ++ else ++ { ++ no_config_param("SPECULATIVE_HARDEN_LOCK", "spec-ctrl", s, ss); ++ rc = -EINVAL; ++ } ++ } + else if ( (val = parse_boolean("srb-lock", s, ss)) >= 0 ) + opt_srb_lock = val; + else if ( (val = parse_boolean("unpriv-mmio", s, ss)) >= 0 ) +@@ -500,7 +512,8 @@ static void __init print_details(enum ind_thunk thunk) + if ( IS_ENABLED(CONFIG_INDIRECT_THUNK) || IS_ENABLED(CONFIG_SHADOW_PAGING) || + IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_ARRAY) || + IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_BRANCH) || +- IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_GUEST_ACCESS) ) ++ IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_GUEST_ACCESS) || ++ IS_ENABLED(CONFIG_SPECULATIVE_HARDEN_LOCK) ) + printk(" Compiled-in support:" + #ifdef CONFIG_INDIRECT_THUNK + " INDIRECT_THUNK" +@@ -516,11 +529,14 @@ static void __init print_details(enum ind_thunk thunk) + #endif + #ifdef CONFIG_SPECULATIVE_HARDEN_GUEST_ACCESS + " HARDEN_GUEST_ACCESS" ++#endif ++#ifdef CONFIG_SPECULATIVE_HARDEN_LOCK ++ " HARDEN_LOCK" + #endif + "\n"); + + /* Settings for Xen's protection, irrespective of guests. */ +- printk(" Xen settings: %s%sSPEC_CTRL: %s%s%s%s%s, Other:%s%s%s%s%s%s\n", ++ printk(" Xen settings: %s%sSPEC_CTRL: %s%s%s%s%s, Other:%s%s%s%s%s%s%s\n", + thunk != THUNK_NONE ? "BTI-Thunk: " : "", + thunk == THUNK_NONE ? "" : + thunk == THUNK_RETPOLINE ? "RETPOLINE, " : +@@ -547,7 +563,8 @@ static void __init print_details(enum ind_thunk thunk) + opt_verw_pv || opt_verw_hvm || + opt_verw_mmio ? " VERW" : "", + opt_div_scrub ? " DIV" : "", +- opt_branch_harden ? " BRANCH_HARDEN" : ""); ++ opt_branch_harden ? " BRANCH_HARDEN" : "", ++ opt_lock_harden ? " LOCK_HARDEN" : ""); + + /* L1TF diagnostics, printed if vulnerable or PV shadowing is in use. */ + if ( cpu_has_bug_l1tf || opt_pv_l1tf_hwdom || opt_pv_l1tf_domu ) +@@ -1930,6 +1947,9 @@ void __init init_speculation_mitigations(void) + if ( !opt_branch_harden ) + setup_force_cpu_cap(X86_FEATURE_SC_NO_BRANCH_HARDEN); + ++ if ( !opt_lock_harden ) ++ setup_force_cpu_cap(X86_FEATURE_SC_NO_LOCK_HARDEN); ++ + /* + * We do not disable HT by default on affected hardware. + * +diff --git a/xen/common/Kconfig b/xen/common/Kconfig +index e7794cb7f6..cd73851538 100644 +--- a/xen/common/Kconfig ++++ b/xen/common/Kconfig +@@ -173,6 +173,23 @@ config SPECULATIVE_HARDEN_GUEST_ACCESS + + If unsure, say Y. + ++config SPECULATIVE_HARDEN_LOCK ++ bool "Speculative lock context hardening" ++ default y ++ depends on X86 ++ help ++ Contemporary processors may use speculative execution as a ++ performance optimisation, but this can potentially be abused by an ++ attacker to leak data via speculative sidechannels. ++ ++ One source of data leakage is via speculative accesses to lock ++ critical regions. ++ ++ This option is disabled by default at run time, and needs to be ++ enabled on the command line. ++ ++ If unsure, say Y. ++ + endmenu + + config DIT_DEFAULT +diff --git a/xen/include/xen/nospec.h b/xen/include/xen/nospec.h +index 76255bc46e..4552846403 100644 +--- a/xen/include/xen/nospec.h ++++ b/xen/include/xen/nospec.h +@@ -70,6 +70,21 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, + #define array_access_nospec(array, index) \ + (array)[array_index_nospec(index, ARRAY_SIZE(array))] + ++static always_inline void block_lock_speculation(void) ++{ ++#ifdef CONFIG_SPECULATIVE_HARDEN_LOCK ++ arch_block_lock_speculation(); ++#endif ++} ++ ++static always_inline bool lock_evaluate_nospec(bool condition) ++{ ++#ifdef CONFIG_SPECULATIVE_HARDEN_LOCK ++ return arch_lock_evaluate_nospec(condition); ++#endif ++ return condition; ++} ++ + #endif /* XEN_NOSPEC_H */ + + /* +diff --git a/xen/include/xen/spinlock.h b/xen/include/xen/spinlock.h +index 961891bea4..daf48fdea7 100644 +--- a/xen/include/xen/spinlock.h ++++ b/xen/include/xen/spinlock.h +@@ -1,6 +1,7 @@ + #ifndef __SPINLOCK_H__ + #define __SPINLOCK_H__ + ++#include <xen/nospec.h> + #include <xen/time.h> + #include <asm/system.h> + #include <asm/spinlock.h> +@@ -189,13 +190,30 @@ int _spin_trylock_recursive(spinlock_t *lock); + void _spin_lock_recursive(spinlock_t *lock); + void _spin_unlock_recursive(spinlock_t *lock); + +-#define spin_lock(l) _spin_lock(l) +-#define spin_lock_cb(l, c, d) _spin_lock_cb(l, c, d) +-#define spin_lock_irq(l) _spin_lock_irq(l) ++static always_inline void spin_lock(spinlock_t *l) ++{ ++ _spin_lock(l); ++ block_lock_speculation(); ++} ++ ++static always_inline void spin_lock_cb(spinlock_t *l, void (*c)(void *data), ++ void *d) ++{ ++ _spin_lock_cb(l, c, d); ++ block_lock_speculation(); ++} ++ ++static always_inline void spin_lock_irq(spinlock_t *l) ++{ ++ _spin_lock_irq(l); ++ block_lock_speculation(); ++} ++ + #define spin_lock_irqsave(l, f) \ + ({ \ + BUILD_BUG_ON(sizeof(f) != sizeof(unsigned long)); \ + ((f) = _spin_lock_irqsave(l)); \ ++ block_lock_speculation(); \ + }) + + #define spin_unlock(l) _spin_unlock(l) +@@ -203,7 +221,7 @@ void _spin_unlock_recursive(spinlock_t *lock); + #define spin_unlock_irqrestore(l, f) _spin_unlock_irqrestore(l, f) + + #define spin_is_locked(l) _spin_is_locked(l) +-#define spin_trylock(l) _spin_trylock(l) ++#define spin_trylock(l) lock_evaluate_nospec(_spin_trylock(l)) + + #define spin_trylock_irqsave(lock, flags) \ + ({ \ +@@ -224,8 +242,15 @@ void _spin_unlock_recursive(spinlock_t *lock); + * are any critical regions that cannot form part of such a set, they can use + * standard spin_[un]lock(). + */ +-#define spin_trylock_recursive(l) _spin_trylock_recursive(l) +-#define spin_lock_recursive(l) _spin_lock_recursive(l) ++#define spin_trylock_recursive(l) \ ++ lock_evaluate_nospec(_spin_trylock_recursive(l)) ++ ++static always_inline void spin_lock_recursive(spinlock_t *l) ++{ ++ _spin_lock_recursive(l); ++ block_lock_speculation(); ++} ++ + #define spin_unlock_recursive(l) _spin_unlock_recursive(l) + + #endif /* __SPINLOCK_H__ */ +-- +2.44.0 + |