x86/bugs: Flush IBP in ib_prctl_set()

stable inclusion
from stable-v4.19.270
commit 940ede60d74d2fc7291b96cb38072d705333c8e0
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/?h=linux-4.19.y&id=940ede60d74d2fc7291b96cb38072d705333c8e0



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commit a664ec91 upstream.

We missed the window between the TIF flag update and the next reschedule.

Signed-off-by: Rodrigo Branco <bsdaemon@google.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yuyao Lin <linyuyao1@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>