[PATCH RFC 23/24] stackdepot: Enable capability analysis

[Marco Elver <elver@google.com>]

Enable capability analysis for stackdepot.

Signed-off-by: Marco Elver <elver@google.com>
---
 lib/Makefile     |  1 +
 lib/stackdepot.c | 24 ++++++++++++++++++------
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/lib/Makefile b/lib/Makefile
index 1dbb59175eb0..f40ba93c9a94 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -270,6 +270,7 @@ obj-$(CONFIG_POLYNOMIAL) += polynomial.o
 # Prevent the compiler from calling builtins like memcmp() or bcmp() from this
 # file.
 CFLAGS_stackdepot.o += -fno-builtin
+CAPABILITY_ANALYSIS_stackdepot.o := y
 obj-$(CONFIG_STACKDEPOT) += stackdepot.o
 KASAN_SANITIZE_stackdepot.o := n
 # In particular, instrumenting stackdepot.c with KMSAN will result in infinite
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 245d5b416699..6664146d1f31 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -14,6 +14,8 @@
 
 #define pr_fmt(fmt) "stackdepot: " fmt
 
+disable_capability_analysis();
+
 #include <linux/debugfs.h>
 #include <linux/gfp.h>
 #include <linux/jhash.h>
@@ -36,6 +38,8 @@
 #include <linux/memblock.h>
 #include <linux/kasan-enabled.h>
 
+enable_capability_analysis();
+
 #define DEPOT_POOLS_CAP 8192
 /* The pool_index is offset by 1 so the first record does not have a 0 handle. */
 #define DEPOT_MAX_POOLS \
@@ -61,18 +65,18 @@ static unsigned int stack_bucket_number_order;
 /* Hash mask for indexing the table. */
 static unsigned int stack_hash_mask;
 
+/* The lock must be held when performing pool or freelist modifications. */
+static DEFINE_RAW_SPINLOCK(pool_lock);
 /* Array of memory regions that store stack records. */
-static void *stack_pools[DEPOT_MAX_POOLS];
+static void *stack_pools[DEPOT_MAX_POOLS] __var_guarded_by(&pool_lock);
 /* Newly allocated pool that is not yet added to stack_pools. */
 static void *new_pool;
 /* Number of pools in stack_pools. */
 static int pools_num;
 /* Offset to the unused space in the currently used pool. */
-static size_t pool_offset = DEPOT_POOL_SIZE;
+static size_t pool_offset __var_guarded_by(&pool_lock) = DEPOT_POOL_SIZE;
 /* Freelist of stack records within stack_pools. */
-static LIST_HEAD(free_stacks);
-/* The lock must be held when performing pool or freelist modifications. */
-static DEFINE_RAW_SPINLOCK(pool_lock);
+static __var_guarded_by(&pool_lock) LIST_HEAD(free_stacks);
 
 /* Statistics counters for debugfs. */
 enum depot_counter_id {
@@ -242,6 +246,7 @@ EXPORT_SYMBOL_GPL(stack_depot_init);
  * Initializes new stack pool, and updates the list of pools.
  */
 static bool depot_init_pool(void **prealloc)
+	__must_hold(&pool_lock)
 {
 	lockdep_assert_held(&pool_lock);
 
@@ -289,6 +294,7 @@ static bool depot_init_pool(void **prealloc)
 
 /* Keeps the preallocated memory to be used for a new stack depot pool. */
 static void depot_keep_new_pool(void **prealloc)
+	__must_hold(&pool_lock)
 {
 	lockdep_assert_held(&pool_lock);
 
@@ -308,6 +314,7 @@ static void depot_keep_new_pool(void **prealloc)
  * the current pre-allocation.
  */
 static struct stack_record *depot_pop_free_pool(void **prealloc, size_t size)
+	__must_hold(&pool_lock)
 {
 	struct stack_record *stack;
 	void *current_pool;
@@ -342,6 +349,7 @@ static struct stack_record *depot_pop_free_pool(void **prealloc, size_t size)
 
 /* Try to find next free usable entry from the freelist. */
 static struct stack_record *depot_pop_free(void)
+	__must_hold(&pool_lock)
 {
 	struct stack_record *stack;
 
@@ -379,6 +387,7 @@ static inline size_t depot_stack_record_size(struct stack_record *s, unsigned in
 /* Allocates a new stack in a stack depot pool. */
 static struct stack_record *
 depot_alloc_stack(unsigned long *entries, unsigned int nr_entries, u32 hash, depot_flags_t flags, void **prealloc)
+	__must_hold(&pool_lock)
 {
 	struct stack_record *stack = NULL;
 	size_t record_size;
@@ -437,6 +446,7 @@ depot_alloc_stack(unsigned long *entries, unsigned int nr_entries, u32 hash, dep
 }
 
 static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)
+	__must_not_hold(&pool_lock)
 {
 	const int pools_num_cached = READ_ONCE(pools_num);
 	union handle_parts parts = { .handle = handle };
@@ -453,7 +463,8 @@ static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)
 		return NULL;
 	}
 
-	pool = stack_pools[pool_index];
+	/* @pool_index either valid, or user passed in corrupted value. */
+	pool = capability_unsafe(stack_pools[pool_index]);
 	if (WARN_ON(!pool))
 		return NULL;
 
@@ -466,6 +477,7 @@ static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)
 
 /* Links stack into the freelist. */
 static void depot_free_stack(struct stack_record *stack)
+	__must_not_hold(&pool_lock)
 {
 	unsigned long flags;
 
-- 
2.48.1.502.g6dc24dfdaf-goog