From cd4d3d5f21ddbfae3f686ac0ff405f21f7847ad3 Mon Sep 17 00:00:00 2001
From: Janosch Frank <frankja@linux.ibm.com>
Date: Tue, 8 Sep 2020 09:05:04 -0400
Subject: [PATCH] s390: add 3f program exception handler
Program exception 3f (secure storage violation) can only be detected
when the CPU is running in SIE with a format 4 state description,
e.g. running a protected guest. Because of this and because user
space partly controls the guest memory mapping and can trigger this
exception, we want to send a SIGSEGV to the process running the guest
and not panic the kernel.
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Cc: <stable@vger.kernel.org> # 5.7
Fixes: 084ea4d611a3 ("s390/mm: add (non)secure page access exceptions handlers")
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
arch/s390/kernel/entry.h | 1 +
arch/s390/kernel/pgm_check.S | 2 +-
arch/s390/mm/fault.c | 20 ++++++++++++++++++++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index faca269d5f2786..a44ddc2f2dec51 100644
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -26,6 +26,7 @@ void do_protection_exception(struct pt_regs *regs);
void do_dat_exception(struct pt_regs *regs);
void do_secure_storage_access(struct pt_regs *regs);
void do_non_secure_storage_access(struct pt_regs *regs);
+void do_secure_storage_violation(struct pt_regs *regs);
void addressing_exception(struct pt_regs *regs);
void data_exception(struct pt_regs *regs);
diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S
index 2c27907a5ffcb8..9a92638360eee6 100644
--- a/arch/s390/kernel/pgm_check.S
+++ b/arch/s390/kernel/pgm_check.S
@@ -80,7 +80,7 @@ PGM_CHECK(do_dat_exception) /* 3b */
PGM_CHECK_DEFAULT /* 3c */
PGM_CHECK(do_secure_storage_access) /* 3d */
PGM_CHECK(do_non_secure_storage_access) /* 3e */
-PGM_CHECK_DEFAULT /* 3f */
+PGM_CHECK(do_secure_storage_violation) /* 3f */
PGM_CHECK(monitor_event_exception) /* 40 */
PGM_CHECK_DEFAULT /* 41 */
PGM_CHECK_DEFAULT /* 42 */
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 4c8c063bce5b16..996884dcc9fdb0 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -859,6 +859,21 @@ void do_non_secure_storage_access(struct pt_regs *regs)
}
NOKPROBE_SYMBOL(do_non_secure_storage_access);
+void do_secure_storage_violation(struct pt_regs *regs)
+{
+ /*
+ * Either KVM messed up the secure guest mapping or the same
+ * page is mapped into multiple secure guests.
+ *
+ * This exception is only triggered when a guest 2 is running
+ * and can therefore never occur in kernel context.
+ */
+ printk_ratelimited(KERN_WARNING
+ "Secure storage violation in task: %s, pid %d\n",
+ current->comm, current->pid);
+ send_sig(SIGSEGV, current, 0);
+}
+
#else
void do_secure_storage_access(struct pt_regs *regs)
{
@@ -869,4 +884,9 @@ void do_non_secure_storage_access(struct pt_regs *regs)
{
default_trap_handler(regs);
}
+
+void do_secure_storage_violation(struct pt_regs *regs)
+{
+ default_trap_handler(regs);
+}
#endif
--
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