Commit d2139ee7 authored by Pan Bian's avatar Pan Bian Committed by Greg Kroah-Hartman

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: 's avatarPan Bian <bianpan2016@163.com>
Signed-off-by: 's avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: 's avatarSasha Levin <sashal@kernel.org>
parent 476a6073
......@@ -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;
}
......
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