From fe0a8a95e7134d0b44cd407bc0085b9ba8d8fe31 Mon Sep 17 00:00:00 2001 From: Lee Duncan Date: Fri, 6 Nov 2020 11:33:17 -0800 Subject: [PATCH 1/2] scsi: libiscsi: Fix NOP race condition iSCSI NOPs are sometimes "lost", mistakenly sent to the user-land iscsid daemon instead of handled in the kernel, as they should be, resulting in a message from the daemon like: iscsid: Got nop in, but kernel supports nop handling. This can occur because of the new forward- and back-locks, and the fact that an iSCSI NOP response can occur before processing of the NOP send is complete. This can result in "conn->ping_task" being NULL in iscsi_nop_out_rsp(), when the pointer is actually in the process of being set. To work around this, we add a new state to the "ping_task" pointer. In addition to NULL (not assigned) and a pointer (assigned), we add the state "being set", which is signaled with an INVALID pointer (using "-1"). Link: https://lore.kernel.org/r/20201106193317.16993-1-leeman.duncan@gmail.com Reviewed-by: Mike Christie Signed-off-by: Lee Duncan Signed-off-by: Martin K. Petersen --- drivers/scsi/libiscsi.c | 23 +++++++++++++++-------- include/scsi/libiscsi.h | 3 +++ 2 files changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c index 1e9c3171fa9f..f9314f1393fb 100644 --- a/drivers/scsi/libiscsi.c +++ b/drivers/scsi/libiscsi.c @@ -533,8 +533,8 @@ static void iscsi_complete_task(struct iscsi_task *task, int state) if (conn->task == task) conn->task = NULL; - if (conn->ping_task == task) - conn->ping_task = NULL; + if (READ_ONCE(conn->ping_task) == task) + WRITE_ONCE(conn->ping_task, NULL); /* release get from queueing */ __iscsi_put_task(task); @@ -738,6 +738,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr, task->conn->session->age); } + if (unlikely(READ_ONCE(conn->ping_task) == INVALID_SCSI_TASK)) + WRITE_ONCE(conn->ping_task, task); + if (!ihost->workq) { if (iscsi_prep_mgmt_task(conn, task)) goto free_task; @@ -941,8 +944,11 @@ 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 -EINVAL; + if (!rhdr) { + if (READ_ONCE(conn->ping_task)) + return -EINVAL; + WRITE_ONCE(conn->ping_task, INVALID_SCSI_TASK); + } memset(&hdr, 0, sizeof(struct iscsi_nopout)); hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE; @@ -957,11 +963,12 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr) task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0); if (!task) { + if (!rhdr) + WRITE_ONCE(conn->ping_task, NULL); iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n"); return -EIO; } else if (!rhdr) { /* only track our nops */ - conn->ping_task = task; conn->last_ping = jiffies; } @@ -984,7 +991,7 @@ static int iscsi_nop_out_rsp(struct iscsi_task *task, struct iscsi_conn *conn = task->conn; int rc = 0; - if (conn->ping_task != task) { + if (READ_ONCE(conn->ping_task) != task) { /* * If this is not in response to one of our * nops then it must be from userspace. @@ -1923,7 +1930,7 @@ static void iscsi_start_tx(struct iscsi_conn *conn) */ static int iscsi_has_ping_timed_out(struct iscsi_conn *conn) { - if (conn->ping_task && + if (READ_ONCE(conn->ping_task) && time_before_eq(conn->last_recv + (conn->recv_timeout * HZ) + (conn->ping_timeout * HZ), jiffies)) return 1; @@ -2058,7 +2065,7 @@ enum blk_eh_timer_return iscsi_eh_cmd_timed_out(struct scsi_cmnd *sc) * Checking the transport already or nop from a cmd timeout still * running */ - if (conn->ping_task) { + if (READ_ONCE(conn->ping_task)) { task->have_checked_conn = true; rc = BLK_EH_RESET_TIMER; goto done; diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h index c25fb86ffae9..b3bbd10eb3f0 100644 --- a/include/scsi/libiscsi.h +++ b/include/scsi/libiscsi.h @@ -132,6 +132,9 @@ struct iscsi_task { void *dd_data; /* driver/transport data */ }; +/* invalid scsi_task pointer */ +#define INVALID_SCSI_TASK (struct iscsi_task *)-1l + static inline int iscsi_task_has_unsol_data(struct iscsi_task *task) { return task->unsol_r2t.data_length > task->unsol_r2t.sent; From f36199355c64a39fe82cfddc7623d827c7e050da Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Fri, 13 Nov 2020 19:46:18 -0600 Subject: [PATCH 2/2] scsi: target: iscsi: Fix cmd abort fabric stop race Maurizio found a race where the abort and cmd stop paths can race as follows: 1. thread1 runs iscsit_release_commands_from_conn and sets CMD_T_FABRIC_STOP. 2. thread2 runs iscsit_aborted_task and then does __iscsit_free_cmd. It then returns from the aborted_task callout and we finish target_handle_abort and do: target_handle_abort -> transport_cmd_check_stop_to_fabric -> lio_check_stop_free -> target_put_sess_cmd The cmd is now freed. 3. thread1 now finishes iscsit_release_commands_from_conn and runs iscsit_free_cmd while accessing a command we just released. In __target_check_io_state we check for CMD_T_FABRIC_STOP and set the CMD_T_ABORTED if the driver is not cleaning up the cmd because of a session shutdown. However, iscsit_release_commands_from_conn only sets the CMD_T_FABRIC_STOP and does not check to see if the abort path has claimed completion ownership of the command. This adds a check in iscsit_release_commands_from_conn so only the abort or fabric stop path cleanup the command. Link: https://lore.kernel.org/r/1605318378-9269-1-git-send-email-michael.christie@oracle.com Reported-by: Maurizio Lombardi Reviewed-by: Maurizio Lombardi Signed-off-by: Mike Christie Signed-off-by: Martin K. Petersen --- drivers/target/iscsi/iscsi_target.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index f77e5eee6b80..518fac4864cf 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -483,8 +483,7 @@ EXPORT_SYMBOL(iscsit_queue_rsp); void iscsit_aborted_task(struct iscsi_conn *conn, struct iscsi_cmd *cmd) { spin_lock_bh(&conn->cmd_lock); - if (!list_empty(&cmd->i_conn_node) && - !(cmd->se_cmd.transport_state & CMD_T_FABRIC_STOP)) + if (!list_empty(&cmd->i_conn_node)) list_del_init(&cmd->i_conn_node); spin_unlock_bh(&conn->cmd_lock); @@ -4083,12 +4082,22 @@ static void iscsit_release_commands_from_conn(struct iscsi_conn *conn) spin_lock_bh(&conn->cmd_lock); list_splice_init(&conn->conn_cmd_list, &tmp_list); - list_for_each_entry(cmd, &tmp_list, i_conn_node) { + list_for_each_entry_safe(cmd, cmd_tmp, &tmp_list, i_conn_node) { struct se_cmd *se_cmd = &cmd->se_cmd; if (se_cmd->se_tfo != NULL) { spin_lock_irq(&se_cmd->t_state_lock); - se_cmd->transport_state |= CMD_T_FABRIC_STOP; + if (se_cmd->transport_state & CMD_T_ABORTED) { + /* + * LIO's abort path owns the cleanup for this, + * so put it back on the list and let + * aborted_task handle it. + */ + list_move_tail(&cmd->i_conn_node, + &conn->conn_cmd_list); + } else { + se_cmd->transport_state |= CMD_T_FABRIC_STOP; + } spin_unlock_irq(&se_cmd->t_state_lock); } }