From nobody Sun Dec 14 05:52:25 2025 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 0FCABC197A0 for ; Mon, 20 Nov 2023 17:51:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231136AbjKTRvv (ORCPT ); Mon, 20 Nov 2023 12:51:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234261AbjKTRvW (ORCPT ); Mon, 20 Nov 2023 12:51:22 -0500 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [IPv6:2001:41d0:203:375::b1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07FB5E3 for ; Mon, 20 Nov 2023 09:50:44 -0800 (PST) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1700502642; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=h9lSbnFVvjj2GZw0LrViVCVgXWgHHPxOTEIrM79fNvQ=; b=altZ3Y/XI4JhIu5hrnCRXA2Lh0EqKL+D8A/MAbLwDHf+SQx3XdzFWHdK500Z2nrgBAdsMJ CIl8i/FRs6CobGUwDDY8obdvF4axa9Jsyq1WLFLLkkvZ3UoyLWEgpJBac7eWWb07xxbTHj /N4UEr5XJVfvRHr9tfyWkhDs5sCw/8o= From: andrey.konovalov@linux.dev To: Andrew Morton Cc: Andrey Konovalov , Marco Elver , Alexander Potapenko , Dmitry Vyukov , Vlastimil Babka , kasan-dev@googlegroups.com, Evgenii Stepanov , Oscar Salvador , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov Subject: [PATCH v4 18/22] kasan: remove atomic accesses to stack ring entries Date: Mon, 20 Nov 2023 18:47:16 +0100 Message-Id: <29f59126d9845c5257b6c29cd7ad113b16f19f47.1700502145.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Andrey Konovalov 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. Reviewed-by: Alexander Potapenko Signed-off-by: Andrey Konovalov --- Changes v1->v2: - This is a new patch. --- mm/kasan/report_tags.c | 25 +++++++------------------ mm/kasan/tags.c | 13 +++++-------- 2 files changed, 12 insertions(+), 26 deletions(-) diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c index 8b8bfdb3cfdb..78abdcde5da9 100644 --- a/mm/kasan/report_tags.c +++ b/mm/kasan/report_tags.c @@ -31,10 +31,6 @@ void kasan_complete_mode_report_info(struct kasan_report= _info *info) 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 =3D false, free_found =3D false; =20 if ((!info->cache || !info->object) && !info->bug_type) { @@ -61,18 +57,11 @@ void kasan_complete_mode_report_info(struct kasan_repor= t_info *info) =20 entry =3D &stack_ring.entries[i % stack_ring.size]; =20 - /* Paired with smp_store_release() in save_stack_info(). */ - ptr =3D (void *)smp_load_acquire(&entry->ptr); - - if (kasan_reset_tag(ptr) !=3D info->object || - get_tag(ptr) !=3D get_tag(info->access_addr)) + if (kasan_reset_tag(entry->ptr) !=3D info->object || + get_tag(entry->ptr) !=3D get_tag(info->access_addr)) continue; =20 - pid =3D READ_ONCE(entry->pid); - stack =3D READ_ONCE(entry->stack); - is_free =3D 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(struct kasan_report_= info *info) if (free_found) break; =20 - info->free_track.pid =3D pid; - info->free_track.stack =3D stack; + info->free_track.pid =3D entry->pid; + info->free_track.stack =3D entry->stack; free_found =3D true; =20 /* @@ -95,8 +84,8 @@ void kasan_complete_mode_report_info(struct kasan_report_= info *info) if (alloc_found) break; =20 - info->alloc_track.pid =3D pid; - info->alloc_track.stack =3D stack; + info->alloc_track.pid =3D entry->pid; + info->alloc_track.stack =3D entry->stack; alloc_found =3D true; =20 /* diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c index 4fd32121b0fd..b6c017e670d8 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -121,15 +121,12 @@ 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. */ =20 - 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 =3D cache->object_size; + entry->pid =3D current->pid; + entry->stack =3D stack; + entry->is_free =3D is_free; =20 - /* - * Paired with smp_load_acquire() in kasan_complete_mode_report_info(). - */ - smp_store_release(&entry->ptr, (s64)object); + entry->ptr =3D object; =20 read_unlock_irqrestore(&stack_ring.lock, flags); } --=20 2.25.1