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>

diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index faca269..a44ddc2 100644 (file)
--- 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 2c27907..9a92638 100644 (file)
--- 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 4c8c063..996884d 100644 (file)
--- 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