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 605CCC636D6 for ; Tue, 31 Jan 2023 00:25:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229723AbjAaAZK (ORCPT ); Mon, 30 Jan 2023 19:25:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229966AbjAaAY5 (ORCPT ); Mon, 30 Jan 2023 19:24:57 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC342193F4 for ; Mon, 30 Jan 2023 16:24:54 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A9000B818BF for ; Tue, 31 Jan 2023 00:24:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4BBFEC433EF; Tue, 31 Jan 2023 00:24:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1675124692; bh=A0lFb252iD9dFfTq7xMmVLzhEvd6Ho0LtGoNTV1QwFI=; h=Date:To:From:Subject:From; b=1BdfYnc8S8KsWPTpw6CQzygqZ7Rq5sIlONZ7mZslFNv3HPu2VCAoAJIWa/xmvLUzx UheI8QbQHb9B3kp7/zCaKi6AisOCi9M4JnzNGBLfvciwJ8ZqBklu4ZuVk+PnwRptDC U9oXT/phBpWRiGGUrhbGx+BOXxDAR8ZONuWQiMwE= Date: Mon, 30 Jan 2023 16:24:51 -0800 To: mm-commits@vger.kernel.org, vbabka@suse.cz, glider@google.com, eugenis@google.com, elver@google.com, andreyknvl@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + lib-stackdepot-annotate-racy-slab_index-accesses.patch added to mm-nonmm-unstable branch Message-Id: <20230131002452.4BBFEC433EF@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: lib/stackdepot: annotate racy slab_index accesses has been added to the -mm mm-nonmm-unstable branch. Its filename is lib-stackdepot-annotate-racy-slab_index-accesses.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-stackdepot-annotate-racy-slab_index-accesses.patch This patch will later appear in the mm-nonmm-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: lib/stackdepot: annotate racy slab_index accesses Date: Mon, 30 Jan 2023 21:49:40 +0100 Accesses to slab_index are protected by slab_lock everywhere except in a sanity check in stack_depot_fetch. The read access there can race with the write access in depot_alloc_stack. Use WRITE/READ_ONCE() to annotate the racy accesses. As the sanity check is only used to print a warning in case of a violation of the stack depot interface usage, it does not make a lot of sense to use proper synchronization. Link: https://lkml.kernel.org/r/19512bb03eed27ced5abeb5bd03f9a8381742cb1.1675111415.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Evgenii Stepanov Cc: Marco Elver Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- --- a/lib/stackdepot.c~lib-stackdepot-annotate-racy-slab_index-accesses +++ a/lib/stackdepot.c @@ -269,8 +269,11 @@ depot_alloc_stack(unsigned long *entries return NULL; } - /* Move on to the next slab. */ - slab_index++; + /* + * Move on to the next slab. + * WRITE_ONCE annotates a race with stack_depot_fetch. + */ + WRITE_ONCE(slab_index, slab_index + 1); slab_offset = 0; /* * smp_store_release() here pairs with smp_load_acquire() in @@ -492,6 +495,8 @@ unsigned int stack_depot_fetch(depot_sta unsigned long **entries) { union handle_parts parts = { .handle = handle }; + /* READ_ONCE annotates a race with depot_alloc_stack. */ + int slab_index_cached = READ_ONCE(slab_index); void *slab; size_t offset = parts.offset << DEPOT_STACK_ALIGN; struct stack_record *stack; @@ -500,9 +505,9 @@ unsigned int stack_depot_fetch(depot_sta if (!handle) return 0; - if (parts.slab_index > slab_index) { + if (parts.slab_index > slab_index_cached) { WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n", - parts.slab_index, slab_index, handle); + parts.slab_index, slab_index_cached, handle); return 0; } slab = stack_slabs[parts.slab_index]; _ Patches currently in -mm which might be from andreyknvl@google.com are kasan-reset-page-tags-properly-with-sampling.patch kasan-reset-page-tags-properly-with-sampling-v2.patch lib-stackdepot-fix-setting-next_slab_inited-in-init_stack_slab.patch lib-stackdepot-put-functions-in-logical-order.patch lib-stackdepot-use-pr_fmt-to-define-message-format.patch lib-stackdepot-mm-rename-stack_depot_want_early_init.patch lib-stackdepot-rename-stack_depot_disable.patch lib-stackdepot-annotate-init-and-early-init-functions.patch lib-stackdepot-lower-the-indentation-in-stack_depot_init.patch lib-stackdepot-reorder-and-annotate-global-variables.patch lib-stackdepot-rename-hash-table-constants-and-variables.patch lib-stackdepot-rename-init_stack_slab.patch lib-stackdepot-rename-slab-variables.patch lib-stackdepot-rename-handle-and-slab-constants.patch lib-stacktrace-drop-impossible-warn_on-for-depot_init_slab.patch lib-stackdepot-annotate-depot_init_slab-and-depot_alloc_stack.patch lib-stacktrace-kasan-kmsan-rework-extra_bits-interface.patch lib-stackdepot-annotate-racy-slab_index-accesses.patch lib-stackdepot-various-comments-clean-ups.patch lib-stackdepot-move-documentation-comments-to-stackdepoth.patch