From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pan Bian , Al Viro , Sasha Levin Subject: [PATCH 4.9 27/51] exportfs: do not read dentry after free Date: Fri, 14 Dec 2018 13:00:29 +0100 Message-Id: <20181214115715.773029553@linuxfoundation.org> In-Reply-To: <20181214115713.244259772@linuxfoundation.org> References: <20181214115713.244259772@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 2084ac6c505a58f7efdec13eba633c6aaa085ca5 ] The function dentry_connected calls dput(dentry) to drop the previously acquired reference to dentry. In this case, dentry can be released. After that, IS_ROOT(dentry) checks the condition (dentry == dentry->d_parent), which may result in a use-after-free bug. This patch directly compares dentry with its parent obtained before dropping the reference. Fixes: a056cc8934c("exportfs: stop retrying once we race with rename/remove") Signed-off-by: Pan Bian Signed-off-by: Al Viro Signed-off-by: Sasha Levin --- fs/exportfs/expfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index a4b531be9168..7a7bba7c2328 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -76,7 +76,7 @@ static bool dentry_connected(struct dentry *dentry) struct dentry *parent = dget_parent(dentry); dput(dentry); - if (IS_ROOT(dentry)) { + if (dentry == parent) { dput(parent); return false; } -- 2.19.1