Merge tag 'kernel-hardening-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kernel hardening updates from Kees Cook:

 - usercopy hardening expanded to check other allocation types (Matthew
   Wilcox, Yuanzheng Song)

 - arm64 stackleak behavioral improvements (Mark Rutland)

 - arm64 CFI code gen improvement (Sami Tolvanen)

 - LoadPin LSM block dev API adjustment (Christoph Hellwig)

 - Clang randstruct support (Bill Wendling, Kees Cook)

* tag 'kernel-hardening-v5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (34 commits)
  loadpin: stop using bdevname
  mm: usercopy: move the virt_addr_valid() below the is_vmalloc_addr()
  gcc-plugins: randstruct: Remove cast exception handling
  af_unix: Silence randstruct GCC plugin warning
  niu: Silence randstruct warnings
  big_keys: Use struct for internal payload
  gcc-plugins: Change all version strings match kernel
  randomize_kstack: Improve docs on requirements/rationale
  lkdtm/stackleak: fix CONFIG_GCC_PLUGIN_STACKLEAK=n
  arm64: entry: use stackleak_erase_on_task_stack()
  stackleak: add on/off stack variants
  lkdtm/stackleak: check stack boundaries
  lkdtm/stackleak: prevent unexpected stack usage
  lkdtm/stackleak: rework boundary management
  lkdtm/stackleak: avoid spurious failure
  stackleak: rework poison scanning
  stackleak: rework stack high bound handling
  stackleak: clarify variable names
  stackleak: rework stack low bound handling
  stackleak: remove redundant check
  ...

8 files changed, 112 insertions, 26 deletions

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index babb1347148c..c84fec767445 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -69,6 +69,16 @@
 #define __nocfi		__attribute__((__no_sanitize__("cfi")))
 #define __cficanonical	__attribute__((__cfi_canonical_jump_table__))
 
+#if defined(CONFIG_CFI_CLANG)
+/*
+ * With CONFIG_CFI_CLANG, the compiler replaces function address
+ * references with the address of the function's CFI jump table
+ * entry. The function_nocfi macro always returns the address of the
+ * actual function instead.
+ */
+#define function_nocfi(x)	__builtin_function_start(x)
+#endif
+
 /*
  * Turn individual warnings and errors on and off locally, depending
  * on version.
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 52299c957c98..a0c55eeaeaf1 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -66,14 +66,6 @@
 		__builtin_unreachable();	\
 	} while (0)
 
-#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
-#define __randomize_layout __attribute__((randomize_layout))
-#define __no_randomize_layout __attribute__((no_randomize_layout))
-/* This anon struct can add padding, so only enable it under randstruct. */
-#define randomized_struct_fields_start	struct {
-#define randomized_struct_fields_end	} __randomize_layout;
-#endif
-
 /*
  * GCC 'asm goto' miscompiles certain code sequences:
  *
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 1c2c33ae1b37..d08dfcb0ac68 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -242,15 +242,15 @@ struct ftrace_likely_data {
 # define __latent_entropy
 #endif
 
-#ifndef __randomize_layout
+#if defined(RANDSTRUCT) && !defined(__CHECKER__)
+# define __randomize_layout __designated_init __attribute__((randomize_layout))
+# define __no_randomize_layout __attribute__((no_randomize_layout))
+/* This anon struct can add padding, so only enable it under randstruct. */
+# define randomized_struct_fields_start	struct {
+# define randomized_struct_fields_end	} __randomize_layout;
+#else
 # define __randomize_layout __designated_init
-#endif
-
-#ifndef __no_randomize_layout
 # define __no_randomize_layout
-#endif
-
-#ifndef randomized_struct_fields_start
 # define randomized_struct_fields_start
 # define randomized_struct_fields_end
 #endif
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index a77be5630209..337bd9f32921 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -149,6 +149,11 @@ static inline void totalhigh_pages_add(long count)
 	atomic_long_add(count, &_totalhigh_pages);
 }
 
+static inline bool is_kmap_addr(const void *x)
+{
+	unsigned long addr = (unsigned long)x;
+	return addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP);
+}
 #else /* CONFIG_HIGHMEM */
 
 static inline struct page *kmap_to_page(void *addr)
@@ -234,6 +239,11 @@ static inline void __kunmap_atomic(void *addr)
 static inline unsigned int nr_free_highpages(void) { return 0; }
 static inline unsigned long totalhigh_pages(void) { return 0UL; }
 
+static inline bool is_kmap_addr(const void *x)
+{
+	return false;
+}
+
 #endif /* CONFIG_HIGHMEM */
 
 /*
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index c7bf1eaf51d5..0c33b715cbfd 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -295,7 +295,7 @@ extern void netfs_stats_show(struct seq_file *);
  */
 static inline struct netfs_i_context *netfs_i_context(struct inode *inode)
 {
-	return (struct netfs_i_context *)(inode + 1);
+	return (void *)inode + sizeof(*inode);
 }
 
 /**
@@ -307,7 +307,7 @@ static inline struct netfs_i_context *netfs_i_context(struct inode *inode)
  */
 static inline struct inode *netfs_inode(struct netfs_i_context *ctx)
 {
-	return ((struct inode *)ctx) - 1;
+	return (void *)ctx - sizeof(struct inode);
 }
 
 /**
diff --git a/include/linux/randomize_kstack.h b/include/linux/randomize_kstack.h
index 1468caf001c0..5d868505a94e 100644
--- a/include/linux/randomize_kstack.h
+++ b/include/linux/randomize_kstack.h
@@ -40,10 +40,14 @@ DECLARE_PER_CPU(u32, kstack_offset);
  */
 #define KSTACK_OFFSET_MAX(x)	((x) & 0x3FF)
 
-/*
- * These macros must be used during syscall entry when interrupts and
+/**
+ * add_random_kstack_offset - Increase stack utilization by previously
+ *			      chosen random offset
+ *
+ * This should be used in the syscall entry path when interrupts and
  * preempt are disabled, and after user registers have been stored to
- * the stack.
+ * the stack. For testing the resulting entropy, please see:
+ * tools/testing/selftests/lkdtm/stack-entropy.sh
  */
 #define add_random_kstack_offset() do {					\
 	if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,	\
@@ -55,6 +59,23 @@ DECLARE_PER_CPU(u32, kstack_offset);
 	}								\
 } while (0)
 
+/**
+ * choose_random_kstack_offset - Choose the random offset for the next
+ *				 add_random_kstack_offset()
+ *
+ * This should only be used during syscall exit when interrupts and
+ * preempt are disabled. This position in the syscall flow is done to
+ * frustrate attacks from userspace attempting to learn the next offset:
+ * - Maximize the timing uncertainty visible from userspace: if the
+ *   offset is chosen at syscall entry, userspace has much more control
+ *   over the timing between choosing offsets. "How long will we be in
+ *   kernel mode?" tends to be more difficult to predict than "how long
+ *   will we be in user mode?"
+ * - Reduce the lifetime of the new offset sitting in memory during
+ *   kernel mode execution. Exposure of "thread-local" memory content
+ *   (e.g. current, percpu, etc) tends to be easier than arbitrary
+ *   location memory exposure.
+ */
 #define choose_random_kstack_offset(rand) do {				\
 	if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,	\
 				&randomize_kstack_offset)) {		\
diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h
index ccaab2043fcd..c36e7a3b45e7 100644
--- a/include/linux/stackleak.h
+++ b/include/linux/stackleak.h
@@ -15,9 +15,62 @@
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
 #include <asm/stacktrace.h>
 
+/*
+ * The lowest address on tsk's stack which we can plausibly erase.
+ */
+static __always_inline unsigned long
+stackleak_task_low_bound(const struct task_struct *tsk)
+{
+	/*
+	 * The lowest unsigned long on the task stack contains STACK_END_MAGIC,
+	 * which we must not corrupt.
+	 */
+	return (unsigned long)end_of_stack(tsk) + sizeof(unsigned long);
+}
+
+/*
+ * The address immediately after the highest address on tsk's stack which we
+ * can plausibly erase.
+ */
+static __always_inline unsigned long
+stackleak_task_high_bound(const struct task_struct *tsk)
+{
+	/*
+	 * The task's pt_regs lives at the top of the task stack and will be
+	 * overwritten by exception entry, so there's no need to erase them.
+	 */
+	return (unsigned long)task_pt_regs(tsk);
+}
+
+/*
+ * Find the address immediately above the poisoned region of the stack, where
+ * that region falls between 'low' (inclusive) and 'high' (exclusive).
+ */
+static __always_inline unsigned long
+stackleak_find_top_of_poison(const unsigned long low, const unsigned long high)
+{
+	const unsigned int depth = STACKLEAK_SEARCH_DEPTH / sizeof(unsigned long);
+	unsigned int poison_count = 0;
+	unsigned long poison_high = high;
+	unsigned long sp = high;
+
+	while (sp > low && poison_count < depth) {
+		sp -= sizeof(unsigned long);
+
+		if (*(unsigned long *)sp == STACKLEAK_POISON) {
+			poison_count++;
+		} else {
+			poison_count = 0;
+			poison_high = sp;
+		}
+	}
+
+	return poison_high;
+}
+
 static inline void stackleak_task_init(struct task_struct *t)
 {
-	t->lowest_stack = (unsigned long)end_of_stack(t) + sizeof(unsigned long);
+	t->lowest_stack = stackleak_task_low_bound(t);
 # ifdef CONFIG_STACKLEAK_METRICS
 	t->prev_lowest_stack = t->lowest_stack;
 # endif
diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
index 329d63babaeb..a54046bf37e5 100644
--- a/include/linux/vermagic.h
+++ b/include/linux/vermagic.h
@@ -32,11 +32,11 @@
 #else
 #define MODULE_VERMAGIC_MODVERSIONS ""
 #endif
-#ifdef RANDSTRUCT_PLUGIN
-#include <generated/randomize_layout_hash.h>
-#define MODULE_RANDSTRUCT_PLUGIN "RANDSTRUCT_PLUGIN_" RANDSTRUCT_HASHED_SEED
+#ifdef RANDSTRUCT
+#include <generated/randstruct_hash.h>
+#define MODULE_RANDSTRUCT "RANDSTRUCT_" RANDSTRUCT_HASHED_SEED
 #else
-#define MODULE_RANDSTRUCT_PLUGIN
+#define MODULE_RANDSTRUCT
 #endif
 
 #define VERMAGIC_STRING 						\
@@ -44,6 +44,6 @@
 	MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT 			\
 	MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS	\
 	MODULE_ARCH_VERMAGIC						\
-	MODULE_RANDSTRUCT_PLUGIN
+	MODULE_RANDSTRUCT
 
 #endif /* _LINUX_VERMAGIC_H */