Commit d2139ee7 authored Nov 23, 2018 by Pan Bian Committed by Greg Kroah-Hartman Dec 17, 2018

exportfs: do not read dentry after free



[ 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: a056cc89("exportfs: stop retrying once we race with
rename/remove")

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 476a6073

fs/exportfs/expfs.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}