[stgt] [PATCH 02/15] Fix use-after-free for task management requests

[Arne Redlich]

If a task management request for a command that is already processed is
received, the tm req will wait for the command to finish. If meanwhile the
connection is closed (as a means of error recovery), the tm req might be
freed prematurely, which will lead to a use-after-free upon completion of the
task.

Signed-off-by: Arne Redlich <arne.redlich at googlemail.com>
---
 usr/iscsi/iscsid.c |   18 +++++++++++++++---
 usr/iscsi/iscsid.h |    1 +
 usr/target.c       |   19 +++++++++++++------
 usr/tgtd.h         |   14 +++++++++++---
 4 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/usr/iscsi/iscsid.c b/usr/iscsi/iscsid.c
index 9252f4a..41e34de 100644
--- a/usr/iscsi/iscsid.c
+++ b/usr/iscsi/iscsid.c
@@ -1325,9 +1325,21 @@ static int iscsi_tm_execute(struct iscsi_task *task)
 
 	if (err)
 		task->result = err;
-	else
-		target_mgmt_request(conn->session->target->tid, conn->session->tsih,
-				    (unsigned long) task, fn, req->lun, req->itt, 0);
+	else {
+		set_task_in_scsi(task);
+		switch (target_mgmt_request(conn->session->target->tid,
+					    conn->session->tsih,
+					    (unsigned long) task, fn, req->lun,
+					    req->itt, 0)) {
+		case MGMT_REQ_QUEUED:
+			break;
+		case MGMT_REQ_FAILED:
+		case MGMT_REQ_DONE:
+			clear_task_in_scsi(task);
+			break;
+		}
+	}
+
 	return err;
 }
 
diff --git a/usr/iscsi/iscsid.h b/usr/iscsi/iscsid.h
index f90e0e9..7897c41 100644
--- a/usr/iscsi/iscsid.h
+++ b/usr/iscsi/iscsid.h
@@ -252,6 +252,7 @@ enum task_flags {
 #define task_pending(t)		((t)->flags & (1 << TASK_pending))
 
 #define set_task_in_scsi(t)     ((t)->flags |= (1 << TASK_in_scsi))
+#define clear_task_in_scsi(t)	((t)->flags &= ~(1 << TASK_in_scsi))
 #define task_in_scsi(t)		((t)->flags & (1 << TASK_in_scsi))
 
 extern int lld_index;
diff --git a/usr/target.c b/usr/target.c
index dc30c87..b7ea99d 100644
--- a/usr/target.c
+++ b/usr/target.c
@@ -1005,8 +1005,10 @@ static int abort_task_set(struct mgmt_req *mreq, struct target* target,
 	return count;
 }
 
-void target_mgmt_request(int tid, uint64_t itn_id, uint64_t req_id,
-			 int function, uint8_t *lun_buf, uint64_t tag, int host_no)
+enum mgmt_req_result target_mgmt_request(int tid, uint64_t itn_id,
+					 uint64_t req_id, int function,
+					 uint8_t *lun_buf, uint64_t tag,
+					 int host_no)
 {
 	struct target *target;
 	struct mgmt_req *mreq;
@@ -1019,12 +1021,15 @@ void target_mgmt_request(int tid, uint64_t itn_id, uint64_t req_id,
 	target = target_lookup(tid);
 	if (!target) {
 		eprintf("invalid tid %d\n", tid);
-		return;
+		return MGMT_REQ_FAILED;
 	}
 
 	mreq = zalloc(sizeof(*mreq));
-	if (!mreq)
-		return;
+	if (!mreq) {
+		eprintf("failed to allocate mgmt_req\n");
+		return MGMT_REQ_FAILED;
+	}
+
 	mreq->mid = req_id;
 	mreq->itn_id = itn_id;
 	mreq->function = function;
@@ -1095,7 +1100,9 @@ void target_mgmt_request(int tid, uint64_t itn_id, uint64_t req_id,
 		mreq->result = err;
 		tgt_drivers[target->lid]->mgmt_end_notify(mreq);
 		free(mreq);
-	}
+		return err ? MGMT_REQ_FAILED : MGMT_REQ_DONE;
+	} else
+		return err ? MGMT_REQ_FAILED : MGMT_REQ_QUEUED;
 }
 
 struct account_entry {
diff --git a/usr/tgtd.h b/usr/tgtd.h
index 12a20dc..303627e 100644
--- a/usr/tgtd.h
+++ b/usr/tgtd.h
@@ -169,6 +169,12 @@ struct mgmt_req {
 	uint64_t itn_id;
 };
 
+enum mgmt_req_result {
+	MGMT_REQ_FAILED = -1,
+	MGMT_REQ_DONE,
+	MGMT_REQ_QUEUED,
+};
+
 #ifdef USE_KERNEL
 extern int kreq_init(void);
 #else
@@ -224,9 +230,11 @@ extern int tgt_event_modify(int fd, int events);
 extern int target_cmd_queue(int tid, struct scsi_cmd *cmd);
 extern void target_cmd_done(struct scsi_cmd *cmd);
 struct scsi_cmd *target_cmd_lookup(int tid, uint64_t itn_id, uint64_t tag);
-extern void target_mgmt_request(int tid, uint64_t itn_id, uint64_t req_id,
-				int function, uint8_t *lun, uint64_t tag,
-				int host_no);
+
+extern enum mgmt_req_result target_mgmt_request(int tid, uint64_t itn_id,
+						uint64_t req_id, int function,
+						uint8_t *lun, uint64_t tag,
+						int host_no);
 
 extern void target_cmd_io_done(struct scsi_cmd *cmd, int result);
 extern int ua_sense_del(struct scsi_cmd *cmd, int del);
-- 
1.6.0.4



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