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 second.openwall.net (second.openwall.net [193.110.157.125]) by smtp.lore.kernel.org (Postfix) with SMTP id 24638C46467 for ; Mon, 16 Jan 2023 19:15:00 +0000 (UTC) Received: (qmail 13727 invoked by uid 550); 16 Jan 2023 19:14:50 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 13690 invoked from network); 16 Jan 2023 19:14:49 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=3I9TKz0QCRwStrORKwRYbo4zYDMGw/8qyv/2PPzcTIw=; b=JhpTDkNcmd/K/PpIamox+UvMbgveXuheag7i9hm8ma5NnX7ZfIOvhDb1HEwnrhqXgV DMPZY4t81B1oRlC1xwXXjkqUDt3e/oxumkm8f58ziGzt6ueDgTdxVpSbxmWLa5Y/LqIP b3h5/Wepronyk03vMqkjLgLzU2Nh6Zcq+b8Ard3BfdYwkBmsxc9039CJba7v7FTcQ6ef 3swlGUN78iSzOIxCdqSboYpAB4+ZEFVbKXJU/A2J4I1H+gpE/GmWLAd7i2MSNVcGX1Jj Dp+HqtxFWRKw2OFt6pSgbCTWBBfOfZmdFLGKnK7jqQS3hYgr3ggvMSbka3FiLg4x9//h b8zg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=3I9TKz0QCRwStrORKwRYbo4zYDMGw/8qyv/2PPzcTIw=; b=6gVbdoX++8p4fpiTVyZ8pLhAK/XPiZTOGj72+FJ9mQcWE2TrEGaY8d9TKs68R7qFVw w/06nwBFnGbAvi/KJ9bg9dvsa2hiMk1ypznGOjNIz8FjPnjhuer0YJvpjttQWcou/zb9 nuKdVlwlbGjgpR7ulqUZcmpGpjS+bCzeTDdbaAKBPxwlfC1mf+aGyo1nhV4DfcrRFD8S MkECS02yrwrAfNLZORlPGrz7nC2PSP3FoA5FzZBNdZjzdcbcke/oU+SqRhO1kzjOgmMM +bNgjWmttutiYrZq86WQnfLJSxNWpDqt8Zkzqn2EplpN2YRSbLfRi+qmRbihrsQYwBX4 waSA== X-Gm-Message-State: AFqh2kq/ax4Pr5Af+aqJpFN/4A70aJCZd9Ft2j3vRMWdpdjMdbfzJxis j0ltPE+dmBUgQ8SWyeWT1dFKZg== X-Google-Smtp-Source: AMrXdXtWSSV63Ld25GuO0BsX3I2Wu43PREgvm5mdCHutcYHBaybO5RRT8NbVv9KhGzTM4D2Fl8Waig== X-Received: by 2002:a05:6000:1d87:b0:2a1:602d:ff3 with SMTP id bk7-20020a0560001d8700b002a1602d0ff3mr1103593wrb.3.1673896478372; Mon, 16 Jan 2023 11:14:38 -0800 (PST) From: Jann Horn To: Alexander Viro , linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH] fs: Use CHECK_DATA_CORRUPTION() when kernel bugs are detected Date: Mon, 16 Jan 2023 20:14:25 +0100 Message-Id: <20230116191425.458864-1-jannh@google.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently, filp_close() and generic_shutdown_super() use printk() to log messages when bugs are detected. This is problematic because infrastructure like syzkaller has no idea that this message indicates a bug. In addition, some people explicitly want their kernels to BUG() when kernel data corruption has been detected (CONFIG_BUG_ON_DATA_CORRUPTION). And finally, when generic_shutdown_super() detects remaining inodes on a system without CONFIG_BUG_ON_DATA_CORRUPTION, it would be nice if later accesses to a busy inode would at least crash somewhat cleanly rather than walking through freed memory. To address all three, use CHECK_DATA_CORRUPTION() when kernel bugs are detected. Signed-off-by: Jann Horn --- fs/open.c | 5 +++-- fs/super.c | 21 +++++++++++++++++---- include/linux/poison.h | 3 +++ 3 files changed, 23 insertions(+), 6 deletions(-) diff --git a/fs/open.c b/fs/open.c index 82c1a28b3308..ceb88ac0ca3b 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1411,8 +1411,9 @@ int filp_close(struct file *filp, fl_owner_t id) { int retval = 0; - if (!file_count(filp)) { - printk(KERN_ERR "VFS: Close: file count is 0\n"); + if (CHECK_DATA_CORRUPTION(file_count(filp) == 0, + "VFS: Close: file count is 0 (f_op=%ps)", + filp->f_op)) { return 0; } diff --git a/fs/super.c b/fs/super.c index 12c08cb20405..cf737ec2bd05 100644 --- a/fs/super.c +++ b/fs/super.c @@ -491,10 +491,23 @@ void generic_shutdown_super(struct super_block *sb) if (sop->put_super) sop->put_super(sb); - if (!list_empty(&sb->s_inodes)) { - printk("VFS: Busy inodes after unmount of %s. " - "Self-destruct in 5 seconds. Have a nice day...\n", - sb->s_id); + if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes), + "VFS: Busy inodes after unmount of %s (%s)", + sb->s_id, sb->s_type->name)) { + /* + * Adding a proper bailout path here would be hard, but + * we can at least make it more likely that a later + * iput_final() or such crashes cleanly. + */ + struct inode *inode; + + spin_lock(&sb->s_inode_list_lock); + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { + inode->i_op = VFS_PTR_POISON; + inode->i_sb = VFS_PTR_POISON; + inode->i_mapping = VFS_PTR_POISON; + } + spin_unlock(&sb->s_inode_list_lock); } } spin_lock(&sb_lock); diff --git a/include/linux/poison.h b/include/linux/poison.h index 2d3249eb0e62..0e8a1f2ceb2f 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -84,4 +84,7 @@ /********** kernel/bpf/ **********/ #define BPF_PTR_POISON ((void *)(0xeB9FUL + POISON_POINTER_DELTA)) +/********** VFS **********/ +#define VFS_PTR_POISON ((void *)(0xF5 + POISON_POINTER_DELTA)) + #endif base-commit: 5dc4c995db9eb45f6373a956eb1f69460e69e6d4 -- 2.39.0.314.g84b9a713c41-goog