From nobody Sun Apr 12 00:54:31 2026 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 C259DC00140 for ; Tue, 2 Aug 2022 15:09:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236360AbiHBPJi (ORCPT ); Tue, 2 Aug 2022 11:09:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237018AbiHBPJd (ORCPT ); Tue, 2 Aug 2022 11:09:33 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 822E52E6B1 for ; Tue, 2 Aug 2022 08:09:31 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Lxyxw12MNzlVp6; Tue, 2 Aug 2022 23:06:44 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 2 Aug 2022 23:09:26 +0800 Received: from localhost.localdomain.localdomain (10.175.113.25) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 2 Aug 2022 23:09:25 +0800 From: Kefeng Wang To: Andrew Morton , CC: , Kefeng Wang , Abhishek Shah , Gabriel Ryan Subject: [PATCH] mm: ksm: fix data-race in __ksm_enter / run_store Date: Tue, 2 Aug 2022 23:15:50 +0800 Message-ID: <20220802151550.159076-1-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.113.25] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Abhishek reported a data-race issue, BUG: KCSAN: data-race in __ksm_enter / run_store write to 0xffffffff881edae0 of 8 bytes by task 6542 on cpu 0: run_store+0x19a/0x2d0 mm/ksm.c:2897 kobj_attr_store+0x44/0x60 lib/kobject.c:824 sysfs_kf_write+0x16f/0x1a0 fs/sysfs/file.c:136 kernfs_fop_write_iter+0x2ae/0x370 fs/kernfs/file.c:291 call_write_iter include/linux/fs.h:2050 [inline] new_sync_write fs/read_write.c:504 [inline] vfs_write+0x779/0x900 fs/read_write.c:591 ksys_write+0xde/0x190 fs/read_write.c:644 __do_sys_write fs/read_write.c:656 [inline] __se_sys_write fs/read_write.c:653 [inline] __x64_sys_write+0x43/0x50 fs/read_write.c:653 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffffffff881edae0 of 8 bytes by task 6541 on cpu 1: __ksm_enter+0x114/0x260 mm/ksm.c:2501 ksm_madvise+0x291/0x350 mm/ksm.c:2451 madvise_vma_behavior mm/madvise.c:1039 [inline] madvise_walk_vmas mm/madvise.c:1221 [inline] do_madvise+0x656/0xeb0 mm/madvise.c:1399 __do_sys_madvise mm/madvise.c:1412 [inline] __se_sys_madvise mm/madvise.c:1410 [inline] __x64_sys_madvise+0x64/0x70 mm/madvise.c:1410 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 6541 Comm: syz-executor2-n Not tainted 5.18.0-rc5+ #107 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/= 2014 The ksm_run is alread protected by ksm_thread_mutex in run_store, we could add this lock in __ksm_enter() to avoid the above issue. Reported-and-tested-by: Abhishek Shah Cc: Gabriel Ryan Signed-off-by: Kefeng Wang --- mm/ksm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index 2f315c69fa2c..3f1908946a6f 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2507,6 +2507,7 @@ int __ksm_enter(struct mm_struct *mm) { struct mm_slot *mm_slot; int needs_wakeup; + bool ksm_run_unmerge; =20 mm_slot =3D alloc_mm_slot(); if (!mm_slot) @@ -2515,6 +2516,10 @@ int __ksm_enter(struct mm_struct *mm) /* Check ksm_run too? Would need tighter locking */ needs_wakeup =3D list_empty(&ksm_mm_head.mm_list); =20 + mutex_lock(&ksm_thread_mutex); + ksm_run_unmerge =3D !!(ksm_run & KSM_RUN_UNMERGE); + mutex_unlock(&ksm_thread_mutex); + spin_lock(&ksm_mmlist_lock); insert_to_mm_slots_hash(mm, mm_slot); /* @@ -2527,7 +2532,7 @@ int __ksm_enter(struct mm_struct *mm) * scanning cursor, otherwise KSM pages in newly forked mms will be * missed: then we might as well insert at the end of the list. */ - if (ksm_run & KSM_RUN_UNMERGE) + if (ksm_run_unmerge) list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); else list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); --=20 2.35.3