From 2084ac6c505a58f7efdec13eba633c6aaa085ca5 Mon Sep 17 00:00:00 2001
From: Pan Bian <bianpan2016@163.com>
Date: Fri, 23 Nov 2018 15:56:33 +0800
Subject: [PATCH] exportfs: do not read dentry after free
Git-commit: 2084ac6c505a58f7efdec13eba633c6aaa085ca5
Patch-mainline: v4.20-rc5
References: bsc#1051510
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 <bianpan2016@163.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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 c8a3dfda1764..c69927bed4ef 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -77,7 +77,7 @@ 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;
}
--
2.16.4