From: Mickaël Salaün <mic@xxxxxxxxxxx> 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@xxxxxxxxxxxxxx Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: Hyunchul Lee <hyc.lee@xxxxxxxxx> Cc: Steve French <smfrench@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20220929100447.108468-1-mic@xxxxxxxxxxx Acked-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> Acked-by: Namjae Jeon <linkinjeon@xxxxxxxxxx> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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@xxxxxxxxxx> */ +#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) {
