kasan: use stack_depot_put for tag-based modes

Make tag-based KASAN modes evict stack traces from the stack depot once
they are evicted from the stack ring.

Internally, pass STACK_DEPOT_FLAG_GET to stack_depot_save_flags (via
kasan_save_stack) to increment the refcount when saving a new entry to
stack ring and call stack_depot_put when removing an entry from stack
ring.

Link: https://lkml.kernel.org/r/b4773e5c1b0b9df6826ec0b65c1923feadfa78e5.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index b6c017e670d8440ea39938fc36ddc41f9581dadc..739ae997463d8d94e1a3e137073706aecc2dc5c8 100644 (file)
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -97,12 +97,13 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
                        gfp_t gfp_flags, bool is_free)
 {
        unsigned long flags;
-       depot_stack_handle_t stack;
+       depot_stack_handle_t stack, old_stack;
        u64 pos;
        struct kasan_stack_ring_entry *entry;
        void *old_ptr;
 
-       stack = kasan_save_stack(gfp_flags, STACK_DEPOT_FLAG_CAN_ALLOC);
+       stack = kasan_save_stack(gfp_flags,
+                       STACK_DEPOT_FLAG_CAN_ALLOC | STACK_DEPOT_FLAG_GET);
 
        /*
         * Prevent save_stack_info() from modifying stack ring
@@ -121,6 +122,8 @@ next:
        if (!try_cmpxchg(&entry->ptr, &old_ptr, STACK_RING_BUSY_PTR))
                goto next; /* Busy slot. */
 
+       old_stack = entry->stack;
+
        entry->size = cache->object_size;
        entry->pid = current->pid;
        entry->stack = stack;
@@ -129,6 +132,9 @@ next:
        entry->ptr = object;
 
        read_unlock_irqrestore(&stack_ring.lock, flags);
+
+       if (old_stack)
+               stack_depot_put(old_stack);
 }
 
 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)