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 E34C1C433EF for ; Wed, 4 May 2022 17:27:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356800AbiEDRa5 (ORCPT ); Wed, 4 May 2022 13:30:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356849AbiEDRJq (ORCPT ); Wed, 4 May 2022 13:09:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4DFC240A33; Wed, 4 May 2022 09:55:59 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id DE080616B8; Wed, 4 May 2022 16:55:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36067C385A5; Wed, 4 May 2022 16:55:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651683358; bh=dF0EmH5rX/p6/vVhDhSdVqRIOShLnMTADUfEzcQ2mgs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Or9WvxCBYZiCJIKgnPUDfxnozzP6msy42wpDgTyZRr2K8yeT0/20w0bDFP6MvwMs/ TWRHH2B1AJGhqvw2n0oLN8UACemwG/LAYi8nPUMR5FGOsqPNySTGe1NTw/ds60RnW6 fkVphcd5050uf/FZd1GX6d1SDQhnGbo0yrAXcjyQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jirka Hladky , Tejun Heo , Minchan Kim Subject: [PATCH 5.17 031/225] kernfs: fix NULL dereferencing in kernfs_remove Date: Wed, 4 May 2022 18:44:29 +0200 Message-Id: <20220504153113.041944007@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220504153110.096069935@linuxfoundation.org> References: <20220504153110.096069935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Minchan Kim commit ad8d869343ae4a07a2038a4ca923f699308c8323 upstream. kernfs_remove supported NULL kernfs_node param to bail out but revent per-fs lock change introduced regression that dereferencing the param without NULL check so kernel goes crash. This patch checks the NULL kernfs_node in kernfs_remove and if so, just return. Quote from bug report by Jirka ``` The bug is triggered by running NAS Parallel benchmark suite on SuperMicro servers with 2x Xeon(R) Gold 6126 CPU. Here is the error log: [ 247.035564] BUG: kernel NULL pointer dereference, address: 0000000000000008 [ 247.036009] #PF: supervisor read access in kernel mode [ 247.036009] #PF: error_code(0x0000) - not-present page [ 247.036009] PGD 0 P4D 0 [ 247.036009] Oops: 0000 [#1] PREEMPT SMP PTI [ 247.058060] CPU: 1 PID: 6546 Comm: umount Not tainted 5.16.0393c3714081a53795bbff0e985d24146def6f57f+ #16 [ 247.058060] Hardware name: Supermicro Super Server/X11DDW-L, BIOS 2.0b 03/07/2018 [ 247.058060] RIP: 0010:kernfs_remove+0x8/0x50 [ 247.058060] Code: 4c 89 e0 5b 5d 41 5c 41 5d 41 5e c3 49 c7 c4 f4 ff ff ff eb b2 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 0f 1f 44 00 00 41 54 55 <48> 8b 47 08 48 89 fd 48 85 c0 48 0f 44 c7 4c 8b 60 50 49 83 c4 60 [ 247.058060] RSP: 0018:ffffbbfa48a27e48 EFLAGS: 00010246 [ 247.058060] RAX: 0000000000000001 RBX: ffffffff89e31f98 RCX: 0000000080200018 [ 247.058060] RDX: 0000000080200019 RSI: fffff6760786c900 RDI: 0000000000000000 [ 247.058060] RBP: ffffffff89e31f98 R08: ffff926b61b24d00 R09: 0000000080200018 [ 247.122048] R10: ffff926b61b24d00 R11: ffff926a8040c000 R12: ffff927bd09a2000 [ 247.122048] R13: ffffffff89e31fa0 R14: dead000000000122 R15: dead000000000100 [ 247.122048] FS: 00007f01be0a8c40(0000) GS:ffff926fa8e40000(0000) knlGS:0000000000000000 [ 247.122048] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 247.122048] CR2: 0000000000000008 CR3: 00000001145c6003 CR4: 00000000007706e0 [ 247.122048] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 247.122048] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 247.122048] PKRU: 55555554 [ 247.122048] Call Trace: [ 247.122048] [ 247.122048] rdt_kill_sb+0x29d/0x350 [ 247.122048] deactivate_locked_super+0x36/0xa0 [ 247.122048] cleanup_mnt+0x131/0x190 [ 247.122048] task_work_run+0x5c/0x90 [ 247.122048] exit_to_user_mode_prepare+0x229/0x230 [ 247.122048] syscall_exit_to_user_mode+0x18/0x40 [ 247.122048] do_syscall_64+0x48/0x90 [ 247.122048] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 247.122048] RIP: 0033:0x7f01be2d735b ``` Link: https://bugzilla.kernel.org/show_bug.cgi?id=215696 Link: https://lore.kernel.org/lkml/CAE4VaGDZr_4wzRn2___eDYRtmdPaGGJdzu_LCSkJYuY9BEO3cw@mail.gmail.com/ Fixes: 393c3714081a (kernfs: switch global kernfs_rwsem lock to per-fs lock) Cc: stable@vger.kernel.org Reported-by: Jirka Hladky Tested-by: Jirka Hladky Acked-by: Tejun Heo Signed-off-by: Minchan Kim Link: https://lore.kernel.org/r/20220427172152.3505364-1-minchan@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/kernfs/dir.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -1397,7 +1397,12 @@ static void __kernfs_remove(struct kernf */ void kernfs_remove(struct kernfs_node *kn) { - struct kernfs_root *root = kernfs_root(kn); + struct kernfs_root *root; + + if (!kn) + return; + + root = kernfs_root(kn); down_write(&root->kernfs_rwsem); __kernfs_remove(kn);