diff mbox series

[v2,19/19] kasan: use stack_depot_put for tag-based modes

Message ID 6e2367e7693aa107f05c649abe06180fff847bb4.1694625260.git.andreyknvl@google.com
State New
Headers
Series stackdepot: allow evicting stack traces |

Commit Message

andrey.konovalov@linux.dev Sept. 13, 2023, 5:14 p.m. UTC 
  From: Andrey Konovalov <andreyknvl@google.com>

Make tag-based KASAN modes to 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.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Changes v1->v2:
- Adapt to the stack depot API change.
- Drop READ_ONCE when reading entry->stack.
---
 mm/kasan/report_tags.c |  1 +
 mm/kasan/tags.c        | 10 ++++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

Comments

Alexander Potapenko Oct. 9, 2023, 12:24 p.m. UTC | #1 
On Wed, Sep 13, 2023 at 7:18 PM <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> Make tag-based KASAN modes to evict stack traces from the stack depot
"Make tag-based KASAN modes evict stack traces from the stack depot"
(without "to")

> 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.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>

(but see the two other comments)

> --- a/mm/kasan/report_tags.c
> +++ b/mm/kasan/report_tags.c
> @@ -7,6 +7,7 @@
>  #include <linux/atomic.h>
>
>  #include "kasan.h"
> +#include "../slab.h"

Why?
Andrey Konovalov Oct. 23, 2023, 4:17 p.m. UTC | #2 
On Mon, Oct 9, 2023 at 2:24 PM Alexander Potapenko <glider@google.com> wrote:
>
> On Wed, Sep 13, 2023 at 7:18 PM <andrey.konovalov@linux.dev> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Make tag-based KASAN modes to evict stack traces from the stack depot
> "Make tag-based KASAN modes evict stack traces from the stack depot"
> (without "to")
>
> > 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.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Reviewed-by: Alexander Potapenko <glider@google.com>
>
> (but see the two other comments)
>
> > --- a/mm/kasan/report_tags.c
> > +++ b/mm/kasan/report_tags.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/atomic.h>
> >
> >  #include "kasan.h"
> > +#include "../slab.h"
>
> Why?

This belongs to the previous patch, will fix in v3, thanks!
diff mbox series

Patch

diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
index 98c238ba3545..55154743f915 100644
--- a/mm/kasan/report_tags.c
+++ b/mm/kasan/report_tags.c
@@ -7,6 +7,7 @@ 
 #include <linux/atomic.h>
 
 #include "kasan.h"
+#include "../slab.h"
 
 extern struct kasan_stack_ring stack_ring;
 
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index b6c017e670d8..739ae997463d 100644
--- 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 @@  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 = entry->stack;
+
 	entry->size = cache->object_size;
 	entry->pid = current->pid;
 	entry->stack = stack;
@@ -129,6 +132,9 @@  static void save_stack_info(struct kmem_cache *cache, void *object,
 	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)