From: Andrey Konovalov <[email protected]>
Evict stack traces from the stack depot for the tag-based KASAN modes
once they are evicted from the stack ring.
Signed-off-by: Andrey Konovalov <[email protected]>
---
mm/kasan/tags.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 7dcfe341d48e..fa6b0f77a7dd 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -96,7 +96,7 @@ 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;
@@ -120,6 +120,8 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
if (!try_cmpxchg(&entry->ptr, &old_ptr, STACK_RING_BUSY_PTR))
goto next; /* Busy slot. */
+ old_stack = READ_ONCE(entry->stack);
+
WRITE_ONCE(entry->size, cache->object_size);
WRITE_ONCE(entry->pid, current->pid);
WRITE_ONCE(entry->stack, stack);
@@ -131,6 +133,9 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
smp_store_release(&entry->ptr, (s64)object);
read_unlock_irqrestore(&stack_ring.lock, flags);
+
+ if (old_stack)
+ stack_depot_evict(old_stack);
}
void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
--
2.25.1
On Mon, Sep 4, 2023 at 8:59 PM Marco Elver <[email protected]> wrote:
>
> >
> > Hm, I actually suspect we don't need these READ/WRITE_ONCE to entry
> > fields at all. This seems to be a leftover from the initial series
> > when I didn't yet have the rwlock. The rwlock prevents the entries
> > from being read (in kasan_complete_mode_report_info) while being
> > written and the try_cmpxchg prevents the same entry from being
> > rewritten (in the unlikely case of wrapping during writing).
> >
> > Marco, do you think we can drop these READ/WRITE_ONCE?
>
> Yes, I think they can be dropped.
Will drop in v2, thanks!