x86/bugs: Flush IBP in ib_prctl_set()

stable inclusion
from stable-v5.10.163
commit 67e39c4f4cb318cfbbf8982ab016c649ed97edaf
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6CU98
CVE: CVE-2023-0045

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=67e39c4f4cb318cfbbf8982ab016c649ed97edaf

--------------------------------

commit a664ec91 upstream.

We missed the window between the TIF flag update and the next reschedule.
Signed-off-by: NRodrigo Branco <bsdaemon@google.com>
Reviewed-by: NBorislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYuyao Lin <linyuyao1@huawei.com>
Reviewed-by: NWang Weiyang <wangweiyang2@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>

arch/x86/kernel/cpu/bugs.c

@@ -1889,6 +1889,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 		if (ctrl == PR_SPEC_FORCE_DISABLE)
 			task_set_spec_ib_force_disable(task);
 		task_update_spec_tif(task);
+		if (task == current)
+			indirect_branch_prediction_barrier();
 		break;
 	default:
 		return -ERANGE;