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Message-ID: <162150613911.29796.9924367580414039528.tip-bot2@tip-bot2>
Date: Thu, 20 May 2021 10:22:19 -0000
From: "tip-bot2 for Joerg Roedel" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
stable@...r.kernel.org, #@...-bot2.tec.linutronix.de,
v5.10+@...-bot2.tec.linutronix.de, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/sev-es: Don't return NULL from sev_es_get_ghcb()
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: b250f2f7792d15bcde98e0456781e2835556d5fa
Gitweb: https://git.kernel.org/tip/b250f2f7792d15bcde98e0456781e2835556d5fa
Author: Joerg Roedel <jroedel@...e.de>
AuthorDate: Wed, 19 May 2021 15:52:44 +02:00
Committer: Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 19 May 2021 17:05:13 +02:00
x86/sev-es: Don't return NULL from sev_es_get_ghcb()
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@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: stable@...r.kernel.org # v5.10+
Link: https://lkml.kernel.org/r/20210519135251.30093-2-joro@8bytes.org
---
arch/x86/kernel/sev.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 4fa111b..82bced8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -203,8 +203,18 @@ static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state)
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;
@@ -1289,7 +1299,6 @@ static __always_inline bool on_vc_fallback_stack(struct pt_regs *regs)
*/
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;
@@ -1315,16 +1324,6 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
*/
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);
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