From 95a520b591c91dd4f78135cecb5eed15707b1a36 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Thu, 29 Sep 2022 12:04:47 +0200 Subject: [PATCH] ksmbd: Fix user namespace mapping MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 7c88c1e0ab1704bacb751341ee6431c3be34b834 upstream. A kernel daemon should not rely on the current thread, which is unknown and might be malicious. Before this security fix, ksmbd_override_fsids() didn't correctly override FS UID/GID which means that arbitrary user space threads could trick the kernel to impersonate arbitrary users or groups for file system access checks, leading to file system access bypass. This was found while investigating truncate support for Landlock: https://lore.kernel.org/r/CAKYAXd8fpMJ7guizOjHgxEyyjoUwPsx3jLOPZP=wPYcbhkVXqA@mail.gmail.com Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: Hyunchul Lee Cc: Steve French Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220929100447.108468-1-mic@digikod.net Acked-by: Christian Brauner (Microsoft) Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/ksmbd/smb_common.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/ksmbd/smb_common.c b/fs/ksmbd/smb_common.c index 31da57d..22f4609 100644 --- a/fs/ksmbd/smb_common.c +++ b/fs/ksmbd/smb_common.c @@ -4,6 +4,8 @@ * Copyright (C) 2018 Namjae Jeon */ +#include + #include "smb_common.h" #include "server.h" #include "misc.h" @@ -624,8 +626,8 @@ int ksmbd_override_fsids(struct ksmbd_work *work) if (!cred) return -ENOMEM; - cred->fsuid = make_kuid(current_user_ns(), uid); - cred->fsgid = make_kgid(current_user_ns(), gid); + cred->fsuid = make_kuid(&init_user_ns, uid); + cred->fsgid = make_kgid(&init_user_ns, gid); gi = groups_alloc(0); if (!gi) { -- 2.7.4