This is a note to let you know that I've just added the patch titled
x86/sev-es: Don't return NULL from sev_es_get_ghcb()
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-don-t-return-null-from-sev_es_get_ghcb.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 b250f2f7792d15bcde98e0456781e2835556d5fa Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@xxxxxxx>
Date: Wed, 19 May 2021 15:52:44 +0200
Subject: x86/sev-es: Don't return NULL from sev_es_get_ghcb()
From: Joerg Roedel <jroedel@xxxxxxx>
commit b250f2f7792d15bcde98e0456781e2835556d5fa upstream.
sev_es_get_ghcb() is called from several places but only one of them
checks the return value. The reaction to returning NULL is always the
same: calling panic() and kill the machine.
Instead of adding checks to all call sites, move the panic() into the
function itself so that it will no longer return NULL.
Fixes: 0786138c78e7 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.10+
Link: https://lkml.kernel.org/r/20210519135251.30093-2-joro@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/sev-es.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -191,8 +191,18 @@ static __always_inline struct ghcb *sev_
if (unlikely(data->ghcb_active)) {
/* GHCB is already in use - save its contents */
- if (unlikely(data->backup_ghcb_active))
- return NULL;
+ if (unlikely(data->backup_ghcb_active)) {
+ /*
+ * Backup-GHCB is also already in use. There is no way
+ * to continue here so just kill the machine. To make
+ * panic() work, mark GHCBs inactive so that messages
+ * can be printed out.
+ */
+ data->ghcb_active = false;
+ data->backup_ghcb_active = false;
+
+ panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");
+ }
/* Mark backup_ghcb active before writing to it */
data->backup_ghcb_active = true;
@@ -1262,7 +1272,6 @@ static __always_inline bool on_vc_fallba
*/
DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
{
- struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
irqentry_state_t irq_state;
struct ghcb_state state;
struct es_em_ctxt ctxt;
@@ -1288,16 +1297,6 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_co
*/
ghcb = sev_es_get_ghcb(&state);
- if (!ghcb) {
- /*
- * Mark GHCBs inactive so that panic() is able to print the
- * message.
- */
- data->ghcb_active = false;
- data->backup_ghcb_active = false;
-
- panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");
- }
vc_ghcb_invalidate(ghcb);
result = vc_init_em_ctxt(&ctxt, regs, error_code);
Patches currently in stable-queue which might be from jroedel@xxxxxxx are
queue-5.10/x86-sev-es-don-t-return-null-from-sev_es_get_ghcb.patch
queue-5.10/x86-sev-es-use-__put_user-__get_user-for-data-accesses.patch
queue-5.10/x86-sev-es-forward-page-faults-which-happen-during-emulation.patch
