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 <[email protected]> Cc: <[email protected]> # 5.7 Fixes: 084ea4d ("s390/mm: add (non)secure page access exceptions handlers") Reviewed-by: Claudio Imbrenda <[email protected]> Reviewed-by: Cornelia Huck <[email protected]> Acked-by: Christian Borntraeger <[email protected]> Signed-off-by: Heiko Carstens <[email protected]> Signed-off-by: Vasily Gorbik <[email protected]>
majek · Sep 14, 2020 · cd4d3d5 · cd4d3d5
1 parent 73ac74c
commit cd4d3d5
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Showing 3 changed files with 22 additions and 1 deletion.
diff --git 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
@@ -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
@@ -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