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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 EC8BCC3B187 for ; Mon, 10 Feb 2020 13:01:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C769C20733 for ; Mon, 10 Feb 2020 13:01:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581339696; bh=VykU2Wi7Q/56cS+dxsozDpC+cSghgfioQCzeX7/+T4M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uemj/O0zVz5gPAq4rqnMRGr252o7nPbnZfDfYPL0XD/1UXFa+e1nEwAlZtYiwJYam R3U5fSIev+d0NFhdqVtAvGmeBFjFQmr7QHfVeq385c2QyZ6ta/P6hMoLQbo2JIqFqS psNt5MGvqSThsLBR3vyiHPhoHAHJNEyAkQ5Yws4o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730495AbgBJNBg (ORCPT ); Mon, 10 Feb 2020 08:01:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:41714 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729812AbgBJMku (ORCPT ); Mon, 10 Feb 2020 07:40:50 -0500 Received: from localhost (unknown [209.37.97.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B12502173E; Mon, 10 Feb 2020 12:40:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338449; bh=VykU2Wi7Q/56cS+dxsozDpC+cSghgfioQCzeX7/+T4M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WdTYxfFzruet6uuoAWkyTif9ByqIqWZtT6+++4FvqW99KOF1dEihWk9rT6hlENSc+ 7b5rpPFPda9Wrp6WibPRYa5o99f0uMBmxGMf0CYMfsNdwhubp9N9t+ApDRQjNq9mK0 S4ujKBx9lyH4uZpMdlesEzD1AODEsAxvZM/H6tvo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , Eric Biggers , Theodore Tso Subject: [PATCH 5.5 194/367] ext4: fix race conditions in ->d_compare() and ->d_hash() Date: Mon, 10 Feb 2020 04:31:47 -0800 Message-Id: <20200210122442.492886906@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200210122423.695146547@linuxfoundation.org> References: <20200210122423.695146547@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Biggers commit ec772f01307a2c06ebf6cdd221e6b518a71ddae7 upstream. 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 Link: https://lore.kernel.org/r/20200124041234.159740-1-ebiggers@kernel.org Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/dir.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -672,9 +672,11 @@ static int ext4_d_compare(const struct d 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); @@ -687,10 +689,11 @@ static int ext4_d_hash(const struct dent { 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);