[tip: x86/urgent] x86/bugs: Flush IBP in ib_prctl_set()

[tip-bot2 for Rodrigo Branco]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     a664ec9158eeddd75121d39c9a0758016097fa96
Gitweb:        https://git.kernel.org/tip/a664ec9158eeddd75121d39c9a0758016097fa96
Author:        Rodrigo Branco <bsdaemon@xxxxxxxxxx>
AuthorDate:    Tue, 03 Jan 2023 14:17:51 -06:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 04 Jan 2023 11:25:32 +01:00

x86/bugs: Flush IBP in ib_prctl_set()

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

Signed-off-by: Rodrigo Branco <bsdaemon@xxxxxxxxxx>
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/bugs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d970ddb..bca0bd8 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1981,6 +1981,8 @@ 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;