From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Mon, 10 Dec 2007 14:06:25 +0100
Subject: [s390] zfcp: fix use after free bug
Message-id: 20071210130625.GH29540@redhat.com
O-Subject: [RHEL5 U2 PATCH 8/8] s390 - zfcp: fix use after free bug.
Bugzilla: 412881
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
============

zfcp_erp_strategy_check_fsfreq() checks if it is safe to access the
fsf_req associated with the erp_action that gets passed. To test if
it is safe it accesses the fsf_req in order to get its index into
the hash list.

This is broken since the fsf_req might be freed already
and the read index has no meaning. It could lead to memory corruption.
Fix this by introducing a new zfcp_reqlist_find_safe() method which
just checks if addresses are equal. This is slower, but only gets
called in case of error recovery.

Bugzilla
=========

BZ 412881
https://bugzilla.redhat.com/show_bug.cgi?id=412881

Upstream status of the patch:
=============================
Posted on linux-scsi
http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11927.html

Test status:
============
Kernel with patch was built and successfully tested

Please ACK.

With best regards,

Hans

diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index 92be569..9ae4907 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -1085,6 +1085,20 @@ extern void _zfcp_hex_dump(char *, int);
 #define zfcp_get_busid_by_port(port) (zfcp_get_busid_by_adapter(port->adapter))
 #define zfcp_get_busid_by_unit(unit) (zfcp_get_busid_by_port(unit->port))
 
+static inline struct zfcp_fsf_req *
+zfcp_reqlist_find_safe(struct zfcp_adapter *adapter, struct zfcp_fsf_req *req)
+{
+	struct zfcp_fsf_req *request;
+	unsigned int idx;
+
+	for (idx = 0; idx < REQUEST_LIST_SIZE; idx++) {
+		list_for_each_entry(request, &adapter->req_list[idx], list)
+			if (request == req)
+				return request;
+	}
+	return NULL;
+}
+
 /*
  *  functions needed for reference/usage counting
  */
diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
index a3e292f..3a3f30b 100644
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -849,8 +849,8 @@ zfcp_erp_strategy_check_fsfreq(struct zfcp_erp_action *erp_action)
 	if (erp_action->fsf_req) {
 		/* take lock to ensure that request is not deleted meanwhile */
 		spin_lock(&adapter->req_list_lock);
-		if (zfcp_reqlist_ismember(adapter,
-					    erp_action->fsf_req->req_id)) {
+		if (zfcp_reqlist_find_safe(adapter, erp_action->fsf_req) &&
+		    erp_action->fsf_req->erp_action == erp_action) {
 			/* fsf_req still exists */
 			debug_text_event(adapter->erp_dbf, 3, "a_ca_req");
 			debug_event(adapter->erp_dbf, 3, &erp_action->fsf_req,