[PATCH RESEND] libiscsi: Fix iscsi_check_transport_timeouts possible infinite loop

[PATCH RESEND] libiscsi: Fix iscsi_check_transport_timeouts possible infinite loop

[Sagi Grimberg]

From: Ariel Nahum <arieln@mellanox.com>

Connection last_ping is not being updated when iscsi_send_nopout fails.
Not updating the last_ping will cause firing a timer to a past time
(last_ping + ping_tmo < current_time) which triggers an infinite loop of
iscsi_check_transport_timeouts() and hogs the cpu.

Fix this issue by checking the return value of iscsi_send_nopout.
If it fails set the next_timeout to one second later.

Signed-off-by: Ariel Nahum <arieln@mellanox.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
---
 drivers/scsi/libiscsi.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 8053f24..29c02b8 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -979,13 +979,13 @@ static void iscsi_tmf_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
 	wake_up(&conn->ehwait);
 }
 
-static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
+static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
 {
         struct iscsi_nopout hdr;
 	struct iscsi_task *task;
 
 	if (!rhdr && conn->ping_task)
-		return;
+		return -EINVAL;
 
 	memset(&hdr, 0, sizeof(struct iscsi_nopout));
 	hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE;
@@ -999,13 +999,16 @@ static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
 		hdr.ttt = RESERVED_ITT;
 
 	task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
-	if (!task)
+	if (!task) {
 		iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n");
-	else if (!rhdr) {
+		return -EIO;
+	} else if (!rhdr) {
 		/* only track our nops */
 		conn->ping_task = task;
 		conn->last_ping = jiffies;
 	}
+
+	return 0;
 }
 
 static int iscsi_nop_out_rsp(struct iscsi_task *task,
@@ -2095,8 +2098,10 @@ static void iscsi_check_transport_timeouts(unsigned long data)
 	if (time_before_eq(last_recv + recv_timeout, jiffies)) {
 		/* send a ping to try to provoke some traffic */
 		ISCSI_DBG_CONN(conn, "Sending nopout as ping\n");
-		iscsi_send_nopout(conn, NULL);
-		next_timeout = conn->last_ping + (conn->ping_timeout * HZ);
+		if (iscsi_send_nopout(conn, NULL))
+			next_timeout = jiffies + (1 * HZ);
+		else
+			next_timeout = conn->last_ping + (conn->ping_timeout * HZ);
 	} else
 		next_timeout = last_recv + recv_timeout;
 
-- 
1.8.4.3

Re: [PATCH RESEND] libiscsi: Fix iscsi_check_transport_timeouts possible infinite loop

[Sagi Grimberg]

On 9/3/2015 7:49 PM, Sagi Grimberg wrote:
> From: Ariel Nahum <arieln@mellanox.com>
>
> Connection last_ping is not being updated when iscsi_send_nopout fails.
> Not updating the last_ping will cause firing a timer to a past time
> (last_ping + ping_tmo < current_time) which triggers an infinite loop of
> iscsi_check_transport_timeouts() and hogs the cpu.
>
> Fix this issue by checking the return value of iscsi_send_nopout.
> If it fails set the next_timeout to one second later.
>
> Signed-off-by: Ariel Nahum <arieln@mellanox.com>
> Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
> Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>

James, can you pick this up please?

Thanks,
Sagi.