Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 63/77] apparmorfs: fix use-after-free on symlink traversal
Date:   Thu, 23 May 2019 21:06:21 +0200
Message-Id: <20190523181728.674674667@linuxfoundation.org>
In-Reply-To: <20190523181719.982121681@linuxfoundation.org>
References: <20190523181719.982121681@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

[ Upstream commit f51dcd0f621caac5380ce90fbbeafc32ce4517ae ]

symlink body shouldn't be freed without an RCU delay.  Switch apparmorfs
to ->destroy_inode() and use of call_rcu(); free both the inode and symlink
body in the callback.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 security/apparmor/apparmorfs.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 0e03377bb83ea..dd746bd69a9b2 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -126,17 +126,22 @@ static int aafs_show_path(struct seq_file *seq, struct dentry *dentry)
 	return 0;
 }
 
-static void aafs_evict_inode(struct inode *inode)
+static void aafs_i_callback(struct rcu_head *head)
 {
-	truncate_inode_pages_final(&inode->i_data);
-	clear_inode(inode);
+	struct inode *inode = container_of(head, struct inode, i_rcu);
 	if (S_ISLNK(inode->i_mode))
 		kfree(inode->i_link);
+	free_inode_nonrcu(inode);
+}
+
+static void aafs_destroy_inode(struct inode *inode)
+{
+	call_rcu(&inode->i_rcu, aafs_i_callback);
 }
 
 static const struct super_operations aafs_super_ops = {
 	.statfs = simple_statfs,
-	.evict_inode = aafs_evict_inode,
+	.destroy_inode = aafs_destroy_inode,
 	.show_path = aafs_show_path,
 };
 
-- 
2.20.1