This is a note to let you know that I've just added the patch titled
x86/sev-es: Invalidate the GHCB after completing VMGEXIT
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-sev-es-invalidate-the-ghcb-after-completing-vmgexit.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a50c5bebc99c525e7fbc059988c6a5ab8680cb76 Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@xxxxxxx>
Date: Mon, 17 May 2021 12:42:33 -0500
Subject: x86/sev-es: Invalidate the GHCB after completing VMGEXIT
From: Tom Lendacky <thomas.lendacky@xxxxxxx>
commit a50c5bebc99c525e7fbc059988c6a5ab8680cb76 upstream.
Since the VMGEXIT instruction can be issued from userspace, invalidate
the GHCB after performing VMGEXIT processing in the kernel.
Invalidation is only required after userspace is available, so call
vc_ghcb_invalidate() from sev_es_put_ghcb(). Update vc_ghcb_invalidate()
to additionally clear the GHCB exit code so that it is always presented
as 0 when VMGEXIT has been issued by anything else besides the kernel.
Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/5a8130462e4f0057ee1184509cd056eedd78742b.1621273353.git.thomas.lendacky@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/sev-es-shared.c | 1 +
arch/x86/kernel/sev-es.c | 5 +++++
2 files changed, 6 insertions(+)
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -63,6 +63,7 @@ static bool sev_es_negotiate_protocol(vo
static __always_inline void vc_ghcb_invalidate(struct ghcb *ghcb)
{
+ ghcb->save.sw_exit_code = 0;
memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
}
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -430,6 +430,11 @@ static __always_inline void sev_es_put_g
data->backup_ghcb_active = false;
state->ghcb = NULL;
} else {
+ /*
+ * Invalidate the GHCB so a VMGEXIT instruction issued
+ * from userspace won't appear to be valid.
+ */
+ vc_ghcb_invalidate(ghcb);
data->ghcb_active = false;
}
}
Patches currently in stable-queue which might be from thomas.lendacky@xxxxxxx are
queue-5.10/x86-sev-es-move-sev_es_put_ghcb-in-prep-for-follow-on-patch.patch
queue-5.10/x86-sev-es-invalidate-the-ghcb-after-completing-vmgexit.patch
