efi/x86: Prevent reentrant firmware calls in mixed mode

The UEFI spec does not permit runtime services to be called
reentrantly, and so it is up to the OS to provide proper locking
around such calls.

For the native case, this was fixed a long time ago, but for the
mixed mode case, no locking is done whatsoever. Note that the calls
are made with preemption and interrupts disabled, so only SMP
configurations are affected by this issue.

So add a spinlock and grab it when invoking a UEFI runtime service
in mixed mode. We will also need to provide non-blocking versions
of SetVariable() and QueryVariableInfo(), so add those as well.
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180720014726.24031-2-ard.biesheuvel@linaro.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/platform/efi/efi_64.c

@@ -636,6 +636,8 @@ void efi_switch_mm(struct mm_struct *mm)
 #ifdef CONFIG_EFI_MIXED
 extern efi_status_t efi64_thunk(u32, ...);
 
+static DEFINE_SPINLOCK(efi_runtime_lock);
+
 #define runtime_service32(func)						 \
 ({									 \
 	u32 table = (u32)(unsigned long)efi.systab;			 \
@@ -657,17 +659,14 @@ extern efi_status_t efi64_thunk(u32, ...);
 #define efi_thunk(f, ...)						\
 ({									\
 	efi_status_t __s;						\
-	unsigned long __flags;						\
 	u32 __func;							\
 									\
-	local_irq_save(__flags);					\
 	arch_efi_call_virt_setup();					\
 									\
 	__func = runtime_service32(f);					\
 	__s = efi64_thunk(__func, __VA_ARGS__);				\
 									\
 	arch_efi_call_virt_teardown();					\
-	local_irq_restore(__flags);					\
 									\
 	__s;								\
 })
@@ -702,14 +701,17 @@ static efi_status_t efi_thunk_get_time(efi_time_t *tm, efi_time_cap_t *tc)
 {
 	efi_status_t status;
 	u32 phys_tm, phys_tc;
+	unsigned long flags;
 
 	spin_lock(&rtc_lock);
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_tm = virt_to_phys_or_null(tm);
 	phys_tc = virt_to_phys_or_null(tc);
 
 	status = efi_thunk(get_time, phys_tm, phys_tc);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
 	spin_unlock(&rtc_lock);
 
 	return status;
@@ -719,13 +721,16 @@ static efi_status_t efi_thunk_set_time(efi_time_t *tm)
 {
 	efi_status_t status;
 	u32 phys_tm;
+	unsigned long flags;
 
 	spin_lock(&rtc_lock);
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_tm = virt_to_phys_or_null(tm);
 
 	status = efi_thunk(set_time, phys_tm);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
 	spin_unlock(&rtc_lock);
 
 	return status;
@@ -737,8 +742,10 @@ efi_thunk_get_wakeup_time(efi_bool_t *enabled, efi_bool_t *pending,
 {
 	efi_status_t status;
 	u32 phys_enabled, phys_pending, phys_tm;
+	unsigned long flags;
 
 	spin_lock(&rtc_lock);
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_enabled = virt_to_phys_or_null(enabled);
 	phys_pending = virt_to_phys_or_null(pending);
@@ -747,6 +754,7 @@ efi_thunk_get_wakeup_time(efi_bool_t *enabled, efi_bool_t *pending,
 	status = efi_thunk(get_wakeup_time, phys_enabled,
 			     phys_pending, phys_tm);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
 	spin_unlock(&rtc_lock);
 
 	return status;
@@ -757,13 +765,16 @@ efi_thunk_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
 {
 	efi_status_t status;
 	u32 phys_tm;
+	unsigned long flags;
 
 	spin_lock(&rtc_lock);
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_tm = virt_to_phys_or_null(tm);
 
 	status = efi_thunk(set_wakeup_time, enabled, phys_tm);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
 	spin_unlock(&rtc_lock);
 
 	return status;
@@ -781,6 +792,9 @@ efi_thunk_get_variable(efi_char16_t *name, efi_guid_t *vendor,
 	efi_status_t status;
 	u32 phys_name, phys_vendor, phys_attr;
 	u32 phys_data_size, phys_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_data_size = virt_to_phys_or_null(data_size);
 	phys_vendor = virt_to_phys_or_null(vendor);
@@ -791,6 +805,8 @@ efi_thunk_get_variable(efi_char16_t *name, efi_guid_t *vendor,
 	status = efi_thunk(get_variable, phys_name, phys_vendor,
 			   phys_attr, phys_data_size, phys_data);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
 	return status;
 }
 
@@ -800,6 +816,34 @@ efi_thunk_set_variable(efi_char16_t *name, efi_guid_t *vendor,
 {
 	u32 phys_name, phys_vendor, phys_data;
 	efi_status_t status;
+	unsigned long flags;
+
+	spin_lock_irqsave(&efi_runtime_lock, flags);
+
+	phys_name = virt_to_phys_or_null_size(name, efi_name_size(name));
+	phys_vendor = virt_to_phys_or_null(vendor);
+	phys_data = virt_to_phys_or_null_size(data, data_size);
+
+	/* If data_size is > sizeof(u32) we've got problems */
+	status = efi_thunk(set_variable, phys_name, phys_vendor,
+			   attr, data_size, phys_data);
+
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
+	return status;
+}
+
+static efi_status_t
+efi_thunk_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
+				   u32 attr, unsigned long data_size,
+				   void *data)
+{
+	u32 phys_name, phys_vendor, phys_data;
+	efi_status_t status;
+	unsigned long flags;
+
+	if (!spin_trylock_irqsave(&efi_runtime_lock, flags))
+		return EFI_NOT_READY;
 
 	phys_name = virt_to_phys_or_null_size(name, efi_name_size(name));
 	phys_vendor = virt_to_phys_or_null(vendor);
@@ -809,6 +853,8 @@ efi_thunk_set_variable(efi_char16_t *name, efi_guid_t *vendor,
 	status = efi_thunk(set_variable, phys_name, phys_vendor,
 			   attr, data_size, phys_data);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
 	return status;
 }
 
@@ -819,6 +865,9 @@ efi_thunk_get_next_variable(unsigned long *name_size,
 {
 	efi_status_t status;
 	u32 phys_name_size, phys_name, phys_vendor;
+	unsigned long flags;
+
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_name_size = virt_to_phys_or_null(name_size);
 	phys_vendor = virt_to_phys_or_null(vendor);
@@ -827,6 +876,8 @@ efi_thunk_get_next_variable(unsigned long *name_size,
 	status = efi_thunk(get_next_variable, phys_name_size,
 			   phys_name, phys_vendor);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
 	return status;
 }
 
@@ -835,10 +886,15 @@ efi_thunk_get_next_high_mono_count(u32 *count)
 {
 	efi_status_t status;
 	u32 phys_count;
+	unsigned long flags;
+
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_count = virt_to_phys_or_null(count);
 	status = efi_thunk(get_next_high_mono_count, phys_count);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
 	return status;
 }
 
@@ -847,10 +903,15 @@ efi_thunk_reset_system(int reset_type, efi_status_t status,
 		       unsigned long data_size, efi_char16_t *data)
 {
 	u32 phys_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&efi_runtime_lock, flags);
 
 	phys_data = virt_to_phys_or_null_size(data, data_size);
 
 	efi_thunk(reset_system, reset_type, status, data_size, phys_data);
+
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
 }
 
 static efi_status_t
@@ -872,10 +933,13 @@ efi_thunk_query_variable_info(u32 attr, u64 *storage_space,
 {
 	efi_status_t status;
 	u32 phys_storage, phys_remaining, phys_max;
+	unsigned long flags;
 
 	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
 		return EFI_UNSUPPORTED;
 
+	spin_lock_irqsave(&efi_runtime_lock, flags);
+
 	phys_storage = virt_to_phys_or_null(storage_space);
 	phys_remaining = virt_to_phys_or_null(remaining_space);
 	phys_max = virt_to_phys_or_null(max_variable_size);
@@ -883,6 +947,35 @@ efi_thunk_query_variable_info(u32 attr, u64 *storage_space,
 	status = efi_thunk(query_variable_info, attr, phys_storage,
 			   phys_remaining, phys_max);
 
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
+	return status;
+}
+
+static efi_status_t
+efi_thunk_query_variable_info_nonblocking(u32 attr, u64 *storage_space,
+					  u64 *remaining_space,
+					  u64 *max_variable_size)
+{
+	efi_status_t status;
+	u32 phys_storage, phys_remaining, phys_max;
+	unsigned long flags;
+
+	if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
+		return EFI_UNSUPPORTED;
+
+	if (!spin_trylock_irqsave(&efi_runtime_lock, flags))
+		return EFI_NOT_READY;
+
+	phys_storage = virt_to_phys_or_null(storage_space);
+	phys_remaining = virt_to_phys_or_null(remaining_space);
+	phys_max = virt_to_phys_or_null(max_variable_size);
+
+	status = efi_thunk(query_variable_info, attr, phys_storage,
+			   phys_remaining, phys_max);
+
+	spin_unlock_irqrestore(&efi_runtime_lock, flags);
+
 	return status;
 }
 
@@ -908,9 +1001,11 @@ void efi_thunk_runtime_setup(void)
 	efi.get_variable = efi_thunk_get_variable;
 	efi.get_next_variable = efi_thunk_get_next_variable;
 	efi.set_variable = efi_thunk_set_variable;
+	efi.set_variable_nonblocking = efi_thunk_set_variable_nonblocking;
 	efi.get_next_high_mono_count = efi_thunk_get_next_high_mono_count;
 	efi.reset_system = efi_thunk_reset_system;
 	efi.query_variable_info = efi_thunk_query_variable_info;
+	efi.query_variable_info_nonblocking = efi_thunk_query_variable_info_nonblocking;
 	efi.update_capsule = efi_thunk_update_capsule;
 	efi.query_capsule_caps = efi_thunk_query_capsule_caps;
 }