[GIT PULL] x86 fixes

Ingo Molnar
2023-09-22T10:33:26Z

Linus,

Please pull the latest x86/urgent git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-urgent-2023-09-22

# HEAD: 509ff51ee652c41a277c2b439aea01a8f56a27b9 x86/shstk: Add warning for shadow stack double unmap

Misc x86 fixes:

- Fix a kexec bug,
- Fix an UML build bug,
- Fix a handful of SRSO related bugs,
- Fix a shadow stacks handling bug & robustify related code.

Thanks,

Ingo

------------------>
Josh Poimboeuf (4):
x86/srso: Fix srso_show_state() side effect
x86/srso: Set CPUID feature bits independently of bug or mitigation status
x86/srso: Don't probe microcode in a guest
x86/srso: Fix SBPB enablement for spec_rstack_overflow=off

Rick Edgecombe (3):
x86/shstk: Handle vfork clone failure correctly
x86/shstk: Remove useless clone error handling
x86/shstk: Add warning for shadow stack double unmap

Rik van Riel (1):
x86/mm, kexec, ima: Use memblock_free_late() from ima_free_kexec_buffer()

Vincent Whitchurch (1):
x86/asm: Fix build of UML with KASAN

arch/x86/include/asm/linkage.h | 7 +++++++
arch/x86/include/asm/mmu_context.h | 3 +--
arch/x86/include/asm/processor.h | 2 --
arch/x86/kernel/cpu/amd.c | 28 +++++++++-------------------
arch/x86/kernel/cpu/bugs.c | 17 +++--------------
arch/x86/kernel/process.c | 7 -------
arch/x86/kernel/setup.c | 8 ++------
arch/x86/kernel/shstk.c | 33 +++++++++++++++++++++++++++++++--
arch/x86/lib/memcpy_64.S | 2 +-
arch/x86/lib/memmove_64.S | 2 +-
arch/x86/lib/memset_64.S | 2 +-
11 files changed, 56 insertions(+), 55 deletions(-)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 5ff49fd67732..571fe4d2d232 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -105,6 +105,13 @@
CFI_POST_PADDING \
SYM_FUNC_END(__cfi_##name)

+/* UML needs to be able to override memcpy() and friends for KASAN. */
+#ifdef CONFIG_UML
+# define SYM_FUNC_ALIAS_MEMFUNC SYM_FUNC_ALIAS_WEAK
+#else
+# define SYM_FUNC_ALIAS_MEMFUNC SYM_FUNC_ALIAS
+#endif
+
/* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
#define SYM_TYPED_FUNC_START(name) \
SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_F_ALIGN) \
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 416901d406f8..8dac45a2c7fc 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -186,8 +186,7 @@ do { \
#else
#define deactivate_mm(tsk, mm) \
do { \
- if (!tsk->vfork_done) \
- shstk_free(tsk); \
+ shstk_free(tsk); \
load_gs_index(0); \
loadsegment(fs, 0); \
} while (0)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0086920cda06..a3669a7774ed 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -683,13 +683,11 @@ extern u16 get_llc_id(unsigned int cpu);
#ifdef CONFIG_CPU_SUP_AMD
extern u32 amd_get_nodes_per_socket(void);
extern u32 amd_get_highest_perf(void);
-extern bool cpu_has_ibpb_brtype_microcode(void);
extern void amd_clear_divider(void);
extern void amd_check_microcode(void);
#else
static inline u32 amd_get_nodes_per_socket(void) { return 0; }
static inline u32 amd_get_highest_perf(void) { return 0; }
-static inline bool cpu_has_ibpb_brtype_microcode(void) { return false; }
static inline void amd_clear_divider(void) { }
static inline void amd_check_microcode(void) { }
#endif
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index dd8379d84445..03ef962a6992 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -766,6 +766,15 @@ static void early_init_amd(struct cpuinfo_x86 *c)

if (cpu_has(c, X86_FEATURE_TOPOEXT))
smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
+
+ if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+ if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
+ setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+ else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
+ setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+ setup_force_cpu_cap(X86_FEATURE_SBPB);
+ }
+ }
}

static void init_amd_k8(struct cpuinfo_x86 *c)
@@ -1301,25 +1310,6 @@ void amd_check_microcode(void)
on_each_cpu(zenbleed_check_cpu, NULL, 1);
}

-bool cpu_has_ibpb_brtype_microcode(void)
-{
- switch (boot_cpu_data.x86) {
- /* Zen1/2 IBPB flushes branch type predictions too. */
- case 0x17:
- return boot_cpu_has(X86_FEATURE_AMD_IBPB);
- case 0x19:
- /* Poke the MSR bit on Zen3/4 to check its presence. */
- if (!wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
- setup_force_cpu_cap(X86_FEATURE_SBPB);
- return true;
- } else {
- return false;
- }
- default:
- return false;
- }
-}
-
/*
* Issue a DIV 0/1 insn to clear any division data from previous DIV
* operations.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f081d26616ac..10499bcd4e39 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2404,26 +2404,15 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);

static void __init srso_select_mitigation(void)
{
- bool has_microcode;
+ bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);

if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
goto pred_cmd;

- /*
- * The first check is for the kernel running as a guest in order
- * for guests to verify whether IBPB is a viable mitigation.
- */
- has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) || cpu_has_ibpb_brtype_microcode();
if (!has_microcode) {
pr_warn("IBPB-extending microcode not applied!\n");
pr_warn(SRSO_NOTICE);
} else {
- /*
- * Enable the synthetic (even if in a real CPUID leaf)
- * flags for guests.
- */
- setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
-
/*
* Zen1/2 with SMT off aren't vulnerable after the right
* IBPB microcode has been applied.
@@ -2444,7 +2433,7 @@ static void __init srso_select_mitigation(void)

switch (srso_cmd) {
case SRSO_CMD_OFF:
- return;
+ goto pred_cmd;

case SRSO_CMD_MICROCODE:
if (has_microcode) {
@@ -2717,7 +2706,7 @@ static ssize_t srso_show_state(char *buf)

return sysfs_emit(buf, "%s%s\n",
srso_strings[srso_mitigation],
- (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
+ boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
}

static ssize_t gds_show_state(char *buf)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9f0909142a0a..b6f4e8399fca 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -257,13 +257,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP)))
io_bitmap_share(p);

- /*
- * If copy_thread() if failing, don't leak the shadow stack possibly
- * allocated in shstk_alloc_thread_stack() above.
- */
- if (ret)
- shstk_free(p);
-
return ret;
}

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index b9145a63da77..b098b1fa2470 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -358,15 +358,11 @@ static void __init add_early_ima_buffer(u64 phys_addr)
#if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE)
int __init ima_free_kexec_buffer(void)
{
- int rc;
-
if (!ima_kexec_buffer_size)
return -ENOENT;

- rc = memblock_phys_free(ima_kexec_buffer_phys,
- ima_kexec_buffer_size);
- if (rc)
- return rc;
+ memblock_free_late(ima_kexec_buffer_phys,
+ ima_kexec_buffer_size);

ima_kexec_buffer_phys = 0;
ima_kexec_buffer_size = 0;
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index fd689921a1db..59e15dd8d0f8 100644
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c
@@ -205,10 +205,21 @@ unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long cl
return 0;

/*
- * For CLONE_VM, except vfork, the child needs a separate shadow
+ * For CLONE_VFORK the child will share the parents shadow stack.
+ * Make sure to clear the internal tracking of the thread shadow
+ * stack so the freeing logic run for child knows to leave it alone.
+ */
+ if (clone_flags & CLONE_VFORK) {
+ shstk->base = 0;
+ shstk->size = 0;
+ return 0;
+ }
+
+ /*
+ * For !CLONE_VM the child will use a copy of the parents shadow
* stack.
*/
- if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM)
+ if (!(clone_flags & CLONE_VM))
return 0;

size = adjust_shstk_size(stack_size);
@@ -408,7 +419,25 @@ void shstk_free(struct task_struct *tsk)
if (!tsk->mm || tsk->mm != current->mm)
return;

+ /*
+ * If shstk->base is NULL, then this task is not managing its
+ * own shadow stack (CLONE_VFORK). So skip freeing it.
+ */
+ if (!shstk->base)
+ return;
+
+ /*
+ * shstk->base is NULL for CLONE_VFORK child tasks, and so is
+ * normal. But size = 0 on a shstk->base is not normal and
+ * indicated an attempt to free the thread shadow stack twice.
+ * Warn about it.
+ */
+ if (WARN_ON(!shstk->size))
+ return;
+
unmap_shadow_stack(shstk->base, shstk->size);
+
+ shstk->size = 0;
}

static int wrss_control(bool enable)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 8f95fb267caa..76697df8dfd5 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -40,7 +40,7 @@ SYM_TYPED_FUNC_START(__memcpy)
SYM_FUNC_END(__memcpy)
EXPORT_SYMBOL(__memcpy)

-SYM_FUNC_ALIAS(memcpy, __memcpy)
+SYM_FUNC_ALIAS_MEMFUNC(memcpy, __memcpy)
EXPORT_SYMBOL(memcpy)

SYM_FUNC_START_LOCAL(memcpy_orig)
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index 0559b206fb11..ccdf3a597045 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -212,5 +212,5 @@ SYM_FUNC_START(__memmove)
SYM_FUNC_END(__memmove)
EXPORT_SYMBOL(__memmove)

-SYM_FUNC_ALIAS(memmove, __memmove)
+SYM_FUNC_ALIAS_MEMFUNC(memmove, __memmove)
EXPORT_SYMBOL(memmove)
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 7c59a704c458..3d818b849ec6 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -40,7 +40,7 @@ SYM_FUNC_START(__memset)
SYM_FUNC_END(__memset)
EXPORT_SYMBOL(__memset)

-SYM_FUNC_ALIAS(memset, __memset)
+SYM_FUNC_ALIAS_MEMFUNC(memset, __memset)
EXPORT_SYMBOL(memset)

SYM_FUNC_START_LOCAL(memset_orig)