The patch titled
Subject: kasan: remove atomic accesses to stack ring entries
has been added to the -mm mm-unstable branch. Its filename is
kasan-remove-atomic-accesses-to-stack-ring-entries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-remove-atomic-accesses-to-stack-ring-entries.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan: remove atomic accesses to stack ring entries
Date: Mon, 20 Nov 2023 18:47:16 +0100
Remove the atomic accesses to entry fields in save_stack_info and
kasan_complete_mode_report_info for tag-based KASAN modes.
These atomics are not required, as the read/write lock prevents the
entries from being read (in kasan_complete_mode_report_info) while being
written (in save_stack_info) and the try_cmpxchg prevents the same entry
from being rewritten (in save_stack_info) in the unlikely case of wrapping
during writing.
Link: https://lkml.kernel.org/r/29f59126d9845c5257b6c29cd7ad113b16f19f47.1700502145.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/report_tags.c | 25 +++++++------------------
mm/kasan/tags.c | 13 +++++--------
2 files changed, 12 insertions(+), 26 deletions(-)
--- a/mm/kasan/report_tags.c~kasan-remove-atomic-accesses-to-stack-ring-entries
+++ a/mm/kasan/report_tags.c
@@ -31,10 +31,6 @@ void kasan_complete_mode_report_info(str
unsigned long flags;
u64 pos;
struct kasan_stack_ring_entry *entry;
- void *ptr;
- u32 pid;
- depot_stack_handle_t stack;
- bool is_free;
bool alloc_found = false, free_found = false;
if ((!info->cache || !info->object) && !info->bug_type) {
@@ -61,18 +57,11 @@ void kasan_complete_mode_report_info(str
entry = &stack_ring.entries[i % stack_ring.size];
- /* Paired with smp_store_release() in save_stack_info(). */
- ptr = (void *)smp_load_acquire(&entry->ptr);
-
- if (kasan_reset_tag(ptr) != info->object ||
- get_tag(ptr) != get_tag(info->access_addr))
+ if (kasan_reset_tag(entry->ptr) != info->object ||
+ get_tag(entry->ptr) != get_tag(info->access_addr))
continue;
- pid = READ_ONCE(entry->pid);
- stack = READ_ONCE(entry->stack);
- is_free = READ_ONCE(entry->is_free);
-
- if (is_free) {
+ if (entry->is_free) {
/*
* Second free of the same object.
* Give up on trying to find the alloc entry.
@@ -80,8 +69,8 @@ void kasan_complete_mode_report_info(str
if (free_found)
break;
- info->free_track.pid = pid;
- info->free_track.stack = stack;
+ info->free_track.pid = entry->pid;
+ info->free_track.stack = entry->stack;
free_found = true;
/*
@@ -95,8 +84,8 @@ void kasan_complete_mode_report_info(str
if (alloc_found)
break;
- info->alloc_track.pid = pid;
- info->alloc_track.stack = stack;
+ info->alloc_track.pid = entry->pid;
+ info->alloc_track.stack = entry->stack;
alloc_found = true;
/*
--- a/mm/kasan/tags.c~kasan-remove-atomic-accesses-to-stack-ring-entries
+++ a/mm/kasan/tags.c
@@ -121,15 +121,12 @@ next:
if (!try_cmpxchg(&entry->ptr, &old_ptr, STACK_RING_BUSY_PTR))
goto next; /* Busy slot. */
- WRITE_ONCE(entry->size, cache->object_size);
- WRITE_ONCE(entry->pid, current->pid);
- WRITE_ONCE(entry->stack, stack);
- WRITE_ONCE(entry->is_free, is_free);
+ entry->size = cache->object_size;
+ entry->pid = current->pid;
+ entry->stack = stack;
+ entry->is_free = is_free;
- /*
- * Paired with smp_load_acquire() in kasan_complete_mode_report_info().
- */
- smp_store_release(&entry->ptr, (s64)object);
+ entry->ptr = object;
read_unlock_irqrestore(&stack_ring.lock, flags);
}
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
lib-stackdepot-print-disabled-message-only-if-truly-disabled.patch
lib-stackdepot-check-disabled-flag-when-fetching.patch
lib-stackdepot-simplify-__stack_depot_save.patch
lib-stackdepot-drop-valid-bit-from-handles.patch
lib-stackdepot-add-depot_fetch_stack-helper.patch
lib-stackdepot-use-fixed-sized-slots-for-stack-records.patch
lib-stackdepot-fix-and-clean-up-atomic-annotations.patch
lib-stackdepot-rework-helpers-for-depot_alloc_stack.patch
lib-stackdepot-rename-next_pool_required-to-new_pool_required.patch
lib-stackdepot-store-next-pool-pointer-in-new_pool.patch
lib-stackdepot-store-free-stack-records-in-a-freelist.patch
lib-stackdepot-use-read-write-lock.patch
lib-stackdepot-use-list_head-for-stack-record-links.patch
kmsan-use-stack_depot_save-instead-of-__stack_depot_save.patch
lib-stackdepot-kasan-add-flags-to-__stack_depot_save-and-rename.patch
lib-stackdepot-add-refcount-for-records.patch
lib-stackdepot-allow-users-to-evict-stack-traces.patch
kasan-remove-atomic-accesses-to-stack-ring-entries.patch
kasan-check-object_size-in-kasan_complete_mode_report_info.patch
kasan-use-stack_depot_put-for-tag-based-modes.patch
kasan-use-stack_depot_put-for-generic-mode.patch
lib-stackdepot-adjust-depot_pools_cap-for-kmsan.patch
