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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 277C2C35242 for ; Fri, 24 Jan 2020 04:14:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE46224125 for ; Fri, 24 Jan 2020 04:14:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579839241; bh=9M/43ASt24xXS4PFNViJs8gRtrsAvfec/+ExbNn5fMI=; h=From:To:Cc:Subject:Date:List-ID:From; b=RiYACe5BGezxUTBZz3eRjLp1ajJ910FWIz6wKCypSBL4npfHjRbfTbuIFbaJNcYNb uN+k6fhuY3NrmIR3meo8ABpKHTEsqVwO3XbX7y9gb6h2AsKxLF+DXjbPPctBi8Q1Cu KgXgQYLlDAVl9eDZueDZ74Di0WmsLZ75i6fcAwo4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729852AbgAXEOA (ORCPT ); Thu, 23 Jan 2020 23:14:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:46622 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729009AbgAXEN7 (ORCPT ); Thu, 23 Jan 2020 23:13:59 -0500 Received: from sol.hsd1.ca.comcast.net (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A22D221835; Fri, 24 Jan 2020 04:13:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579839238; bh=9M/43ASt24xXS4PFNViJs8gRtrsAvfec/+ExbNn5fMI=; h=From:To:Cc:Subject:Date:From; b=ENYOqfwbD3Idoo/SDprBeK4AfVugyAXIQatJ4WXhb7ShxC3xiI7JvGlp6wWT22RpC BKf+zdUm+zUkIb92mRSPKwYfoRygux1T+WH/QpL58S5C7fEEu+F80szSGoKL+e5ECE m3yYsYGScHTZNz3X2QwyDjT179CYPDFaRbZmgHpM= From: Eric Biggers To: linux-ext4@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Alexander Viro , Daniel Rosenberg , Gabriel Krisman Bertazi Subject: [PATCH] ext4: fix race conditions in ->d_compare() and ->d_hash() Date: Thu, 23 Jan 2020 20:12:34 -0800 Message-Id: <20200124041234.159740-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Eric Biggers Since ->d_compare() and ->d_hash() can be called in RCU-walk mode, ->d_parent and ->d_inode can be concurrently modified, and in particular, ->d_inode may be changed to NULL. For ext4_d_hash() this resulted in a reproducible NULL dereference if a lookup is done in a directory being deleted, e.g. with: int main() { if (fork()) { for (;;) { mkdir("subdir", 0700); rmdir("subdir"); } } else { for (;;) access("subdir/file", 0); } } ... or by running the 't_encrypted_d_revalidate' program from xfstests. Both repros work in any directory on a filesystem with the encoding feature, even if the directory doesn't actually have the casefold flag. I couldn't reproduce a crash in ext4_d_compare(), but it appears that a similar crash is possible there. Fix these bugs by reading ->d_parent and ->d_inode using READ_ONCE() and falling back to the case sensitive behavior if the inode is NULL. Reported-by: Al Viro Fixes: b886ee3e778e ("ext4: Support case-insensitive file name lookups") Cc: # v5.2+ Signed-off-by: Eric Biggers --- fs/ext4/dir.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index 8964778aabefb..0129d14629881 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -671,9 +671,11 @@ static int ext4_d_compare(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { struct qstr qstr = {.name = str, .len = len }; - struct inode *inode = dentry->d_parent->d_inode; + const struct dentry *parent = READ_ONCE(dentry->d_parent); + const struct inode *inode = READ_ONCE(parent->d_inode); - if (!IS_CASEFOLDED(inode) || !EXT4_SB(inode->i_sb)->s_encoding) { + if (!inode || !IS_CASEFOLDED(inode) || + !EXT4_SB(inode->i_sb)->s_encoding) { if (len != name->len) return -1; return memcmp(str, name->name, len); @@ -686,10 +688,11 @@ static int ext4_d_hash(const struct dentry *dentry, struct qstr *str) { const struct ext4_sb_info *sbi = EXT4_SB(dentry->d_sb); const struct unicode_map *um = sbi->s_encoding; + const struct inode *inode = READ_ONCE(dentry->d_inode); unsigned char *norm; int len, ret = 0; - if (!IS_CASEFOLDED(dentry->d_inode) || !um) + if (!inode || !IS_CASEFOLDED(inode) || !um) return 0; norm = kmalloc(PATH_MAX, GFP_ATOMIC); -- 2.25.0