From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51F2AEE0207 for ; Wed, 13 Sep 2023 19:29:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231980AbjIMT3c (ORCPT ); Wed, 13 Sep 2023 15:29:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232492AbjIMT3R (ORCPT ); Wed, 13 Sep 2023 15:29:17 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B8C861998 for ; Wed, 13 Sep 2023 12:29:13 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53D2AC433C8; Wed, 13 Sep 2023 19:29:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1694633353; bh=7T7UMrgm8bqEL/S9ExnNWyXr7s/KPScBFqtWM8ZS4IM=; h=Date:To:From:Subject:From; b=OHgHSXQH/SzcyS4Q7UZt4TcHJS1yvCADFHR0MjCjvfuP1Qvc/vpJyV+fdrDLPeiXz dMMeuPzFK7+Nd8YrgISCY17jiX1o2UrpAOUEZTk+0ZjD5bzznjyoPTIVGgaUQv6RGf XETVvuBWxIqYfk7SmmxTxgLvK+xTBqofTomGdbQ0= Date: Wed, 13 Sep 2023 12:29:12 -0700 To: mm-commits@vger.kernel.org, vbabka@suse.cz, osalvador@suse.de, glider@google.com, eugenis@google.com, elver@google.com, dvyukov@google.com, andreyknvl@gmail.com, andreyknvl@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + kasan-remove-atomic-accesses-to-stack-ring-entries.patch added to mm-unstable branch Message-Id: <20230913192913.53D2AC433C8@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org 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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Andrey Konovalov Subject: kasan: remove atomic accesses to stack ring entries Date: Wed, 13 Sep 2023 19:14:42 +0200 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/556085476eb7d2e3703d62dc2fa920931aadf459.1694625260.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Marco Elver Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- 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@google.com are 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