From: Mickaël Salaün mic@digikod.net
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=wPYcbhkVXq...
Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: Hyunchul Lee hyc.lee@gmail.com Cc: Steve French smfrench@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün mic@digikod.net Link: https://lore.kernel.org/r/20220929100447.108468-1-mic@digikod.net Acked-by: Christian Brauner (Microsoft) brauner@kernel.org Acked-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ksmbd/smb_common.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/ksmbd/smb_common.c +++ b/fs/ksmbd/smb_common.c @@ -4,6 +4,8 @@ * Copyright (C) 2018 Namjae Jeon linkinjeon@kernel.org */
+#include <linux/user_namespace.h> + #include "smb_common.h" #include "server.h" #include "misc.h" @@ -625,8 +627,8 @@ int ksmbd_override_fsids(struct ksmbd_wo 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) {