[PATCH] s390: cmm guest sender id

An arbitrary guest must not be allowed to trigger cmm actions.  Only one
specific guest namely the one that serves as the resource monitor may send cmm
messages.  Add a parameter that allows to specify the guest that may send
messages.  z/VMs resource manager has the name 'VMRMSVM' which is the default.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/mm/cmm.c

@@ -20,6 +20,11 @@
 #include <asm/pgalloc.h>
 #include <asm/uaccess.h>
 
+static char *sender = "VMRMSVM";
+module_param(sender, charp, 0);
+MODULE_PARM_DESC(sender,
+		 "Guest name that may send SMSG messages (default VMRMSVM)");
+
 #include "../../../drivers/s390/net/smsgiucv.h"
 
 #define CMM_NR_PAGES ((PAGE_SIZE / sizeof(unsigned long)) - 2)
@@ -367,10 +372,12 @@ static struct ctl_table cmm_dir_table[] = {
 #ifdef CONFIG_CMM_IUCV
 #define SMSG_PREFIX "CMM"
 static void
-cmm_smsg_target(char *msg)
+cmm_smsg_target(char *from, char *msg)
 {
 	long pages, seconds;
 
+	if (strlen(sender) > 0 && strcmp(from, sender) != 0)
+		return;
 	if (!cmm_skip_blanks(msg + strlen(SMSG_PREFIX), &msg))
 		return;
 	if (strncmp(msg, "SHRINK", 6) == 0) {

drivers/s390/net/smsgiucv.c

@@ -32,7 +32,7 @@ struct smsg_callback {
 	struct list_head list;
 	char *prefix;
 	int len;
-	void (*callback)(char *str);
+	void (*callback)(char *from, char *str);
 };
 
 MODULE_AUTHOR
@@ -55,8 +55,9 @@ smsg_message_pending(iucv_MessagePending *eib, void *pgm_data)
 {
 	struct smsg_callback *cb;
 	unsigned char *msg;
+	unsigned char sender[9];
 	unsigned short len;
-	int rc;
+	int rc, i;
 
 	len = eib->ln1msg2.ipbfln1f;
 	msg = kmalloc(len + 1, GFP_ATOMIC|GFP_DMA);
@@ -69,10 +70,18 @@ smsg_message_pending(iucv_MessagePending *eib, void *pgm_data)
 	if (rc == 0) {
 		msg[len] = 0;
 		EBCASC(msg, len);
+		memcpy(sender, msg, 8);
+		sender[8] = 0;
+		/* Remove trailing whitespace from the sender name. */
+		for (i = 7; i >= 0; i--) {
+			if (sender[i] != ' ' && sender[i] != '\t')
+				break;
+			sender[i] = 0;
+		}
 		spin_lock(&smsg_list_lock);
 		list_for_each_entry(cb, &smsg_list, list)
 			if (strncmp(msg + 8, cb->prefix, cb->len) == 0) {
-				cb->callback(msg + 8);
+				cb->callback(sender, msg + 8);
 				break;
 			}
 		spin_unlock(&smsg_list_lock);
@@ -91,7 +100,7 @@ static struct device_driver smsg_driver = {
 };
 
 int
-smsg_register_callback(char *prefix, void (*callback)(char *str))
+smsg_register_callback(char *prefix, void (*callback)(char *from, char *str))
 {
 	struct smsg_callback *cb;
 
@@ -108,7 +117,7 @@ smsg_register_callback(char *prefix, void (*callback)(char *str))
 }
 
 void
-smsg_unregister_callback(char *prefix, void (*callback)(char *str))
+smsg_unregister_callback(char *prefix, void (*callback)(char *from, char *str))
 {
 	struct smsg_callback *cb, *tmp;
 

drivers/s390/net/smsgiucv.h

@@ -5,6 +5,6 @@
  * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
  */
 
-int  smsg_register_callback(char *, void (*)(char *));
-void smsg_unregister_callback(char *, void (*)(char *));
+int  smsg_register_callback(char *, void (*)(char *, char *));
+void smsg_unregister_callback(char *, void (*)(char *, char *));