From 4eb2095c80a56fec125c06465a2f61dcc3ed5369 Mon Sep 17 00:00:00 2001 From: Pan Bian Date: Fri, 23 Nov 2018 15:56:33 +0800 Subject: [PATCH] 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: 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 a3aa6ba..d4dcf3c 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; } -- 2.7.4