From 25cdda95fda78d22d44157da15aa7ea34be3c804 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Wed, 24 May 2017 21:47:09 -0700 Subject: [PATCH] iscsi-target: Fix initial login PDU asynchronous socket close OOPs This patch fixes a OOPs originally introduced by: commit bb048357dad6d604520c91586334c9c230366a14 Author: Nicholas Bellinger Date: Thu Sep 5 14:54:04 2013 -0700 iscsi-target: Add sk->sk_state_change to cleanup after TCP failure which would trigger a NULL pointer dereference when a TCP connection was closed asynchronously via iscsi_target_sk_state_change(), but only when the initial PDU processing in iscsi_target_do_login() from iscsi_np process context was blocked waiting for backend I/O to complete. To address this issue, this patch makes the following changes. First, it introduces some common helper functions used for checking socket closing state, checking login_flags, and atomically checking socket closing state + setting login_flags. Second, it introduces a LOGIN_FLAGS_INITIAL_PDU bit to know when a TCP connection has dropped via iscsi_target_sk_state_change(), but the initial PDU processing within iscsi_target_do_login() in iscsi_np context is still running. For this case, it sets LOGIN_FLAGS_CLOSED, but doesn't invoke schedule_delayed_work(). The original NULL pointer dereference case reported by MNC is now handled by iscsi_target_do_login() doing a iscsi_target_sk_check_close() before transitioning to FFP to determine when the socket has already closed, or iscsi_target_start_negotiation() if the login needs to exchange more PDUs (eg: iscsi_target_do_login returned 0) but the socket has closed. For both of these cases, the cleanup up of remaining connection resources will occur in iscsi_target_start_negotiation() from iscsi_np process context once the failure is detected. Finally, to handle to case where iscsi_target_sk_state_change() is called after the initial PDU procesing is complete, it now invokes conn->login_work -> iscsi_target_do_login_rx() to perform cleanup once existing iscsi_target_sk_check_close() checks detect connection failure. For this case, the cleanup of remaining connection resources will occur in iscsi_target_do_login_rx() from delayed workqueue process context once the failure is detected. Reported-by: Mike Christie Reviewed-by: Mike Christie Tested-by: Mike Christie Cc: Mike Christie Reported-by: Hannes Reinecke Cc: Hannes Reinecke Cc: Sagi Grimberg Cc: Varun Prakash Cc: # v3.12+ Signed-off-by: Nicholas Bellinger --- drivers/target/iscsi/iscsi_target_nego.c | 194 +++++++++++++++-------- include/target/iscsi/iscsi_target_core.h | 1 + 2 files changed, 133 insertions(+), 62 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c index 7ccc9c1cbfd1..6f88b31242b0 100644 --- a/drivers/target/iscsi/iscsi_target_nego.c +++ b/drivers/target/iscsi/iscsi_target_nego.c @@ -493,14 +493,60 @@ static void iscsi_target_restore_sock_callbacks(struct iscsi_conn *conn) static int iscsi_target_do_login(struct iscsi_conn *, struct iscsi_login *); -static bool iscsi_target_sk_state_check(struct sock *sk) +static bool __iscsi_target_sk_check_close(struct sock *sk) { if (sk->sk_state == TCP_CLOSE_WAIT || sk->sk_state == TCP_CLOSE) { - pr_debug("iscsi_target_sk_state_check: TCP_CLOSE_WAIT|TCP_CLOSE," + pr_debug("__iscsi_target_sk_check_close: TCP_CLOSE_WAIT|TCP_CLOSE," "returning FALSE\n"); - return false; + return true; } - return true; + return false; +} + +static bool iscsi_target_sk_check_close(struct iscsi_conn *conn) +{ + bool state = false; + + if (conn->sock) { + struct sock *sk = conn->sock->sk; + + read_lock_bh(&sk->sk_callback_lock); + state = (__iscsi_target_sk_check_close(sk) || + test_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags)); + read_unlock_bh(&sk->sk_callback_lock); + } + return state; +} + +static bool iscsi_target_sk_check_flag(struct iscsi_conn *conn, unsigned int flag) +{ + bool state = false; + + if (conn->sock) { + struct sock *sk = conn->sock->sk; + + read_lock_bh(&sk->sk_callback_lock); + state = test_bit(flag, &conn->login_flags); + read_unlock_bh(&sk->sk_callback_lock); + } + return state; +} + +static bool iscsi_target_sk_check_and_clear(struct iscsi_conn *conn, unsigned int flag) +{ + bool state = false; + + if (conn->sock) { + struct sock *sk = conn->sock->sk; + + write_lock_bh(&sk->sk_callback_lock); + state = (__iscsi_target_sk_check_close(sk) || + test_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags)); + if (!state) + clear_bit(flag, &conn->login_flags); + write_unlock_bh(&sk->sk_callback_lock); + } + return state; } static void iscsi_target_login_drop(struct iscsi_conn *conn, struct iscsi_login *login) @@ -540,6 +586,20 @@ static void iscsi_target_do_login_rx(struct work_struct *work) pr_debug("entering iscsi_target_do_login_rx, conn: %p, %s:%d\n", conn, current->comm, current->pid); + /* + * If iscsi_target_do_login_rx() has been invoked by ->sk_data_ready() + * before initial PDU processing in iscsi_target_start_negotiation() + * has completed, go ahead and retry until it's cleared. + * + * Otherwise if the TCP connection drops while this is occuring, + * iscsi_target_start_negotiation() will detect the failure, call + * cancel_delayed_work_sync(&conn->login_work), and cleanup the + * remaining iscsi connection resources from iscsi_np process context. + */ + if (iscsi_target_sk_check_flag(conn, LOGIN_FLAGS_INITIAL_PDU)) { + schedule_delayed_work(&conn->login_work, msecs_to_jiffies(10)); + return; + } spin_lock(&tpg->tpg_state_lock); state = (tpg->tpg_state == TPG_STATE_ACTIVE); @@ -547,26 +607,12 @@ static void iscsi_target_do_login_rx(struct work_struct *work) if (!state) { pr_debug("iscsi_target_do_login_rx: tpg_state != TPG_STATE_ACTIVE\n"); - iscsi_target_restore_sock_callbacks(conn); - iscsi_target_login_drop(conn, login); - iscsit_deaccess_np(np, tpg, tpg_np); - return; + goto err; } - if (conn->sock) { - struct sock *sk = conn->sock->sk; - - read_lock_bh(&sk->sk_callback_lock); - state = iscsi_target_sk_state_check(sk); - read_unlock_bh(&sk->sk_callback_lock); - - if (!state) { - pr_debug("iscsi_target_do_login_rx, TCP state CLOSE\n"); - iscsi_target_restore_sock_callbacks(conn); - iscsi_target_login_drop(conn, login); - iscsit_deaccess_np(np, tpg, tpg_np); - return; - } + if (iscsi_target_sk_check_close(conn)) { + pr_debug("iscsi_target_do_login_rx, TCP state CLOSE\n"); + goto err; } conn->login_kworker = current; @@ -584,34 +630,29 @@ static void iscsi_target_do_login_rx(struct work_struct *work) flush_signals(current); conn->login_kworker = NULL; - if (rc < 0) { - iscsi_target_restore_sock_callbacks(conn); - iscsi_target_login_drop(conn, login); - iscsit_deaccess_np(np, tpg, tpg_np); - return; - } + if (rc < 0) + goto err; pr_debug("iscsi_target_do_login_rx after rx_login_io, %p, %s:%d\n", conn, current->comm, current->pid); rc = iscsi_target_do_login(conn, login); if (rc < 0) { - iscsi_target_restore_sock_callbacks(conn); - iscsi_target_login_drop(conn, login); - iscsit_deaccess_np(np, tpg, tpg_np); + goto err; } else if (!rc) { - if (conn->sock) { - struct sock *sk = conn->sock->sk; - - write_lock_bh(&sk->sk_callback_lock); - clear_bit(LOGIN_FLAGS_READ_ACTIVE, &conn->login_flags); - write_unlock_bh(&sk->sk_callback_lock); - } + if (iscsi_target_sk_check_and_clear(conn, LOGIN_FLAGS_READ_ACTIVE)) + goto err; } else if (rc == 1) { iscsi_target_nego_release(conn); iscsi_post_login_handler(np, conn, zero_tsih); iscsit_deaccess_np(np, tpg, tpg_np); } + return; + +err: + iscsi_target_restore_sock_callbacks(conn); + iscsi_target_login_drop(conn, login); + iscsit_deaccess_np(np, tpg, tpg_np); } static void iscsi_target_do_cleanup(struct work_struct *work) @@ -659,31 +700,54 @@ static void iscsi_target_sk_state_change(struct sock *sk) orig_state_change(sk); return; } + state = __iscsi_target_sk_check_close(sk); + pr_debug("__iscsi_target_sk_close_change: state: %d\n", state); + if (test_bit(LOGIN_FLAGS_READ_ACTIVE, &conn->login_flags)) { pr_debug("Got LOGIN_FLAGS_READ_ACTIVE=1 sk_state_change" " conn: %p\n", conn); + if (state) + set_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags); write_unlock_bh(&sk->sk_callback_lock); orig_state_change(sk); return; } - if (test_and_set_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags)) { + if (test_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags)) { pr_debug("Got LOGIN_FLAGS_CLOSED=1 sk_state_change conn: %p\n", conn); write_unlock_bh(&sk->sk_callback_lock); orig_state_change(sk); return; } + /* + * If the TCP connection has dropped, go ahead and set LOGIN_FLAGS_CLOSED, + * but only queue conn->login_work -> iscsi_target_do_login_rx() + * processing if LOGIN_FLAGS_INITIAL_PDU has already been cleared. + * + * When iscsi_target_do_login_rx() runs, iscsi_target_sk_check_close() + * will detect the dropped TCP connection from delayed workqueue context. + * + * If LOGIN_FLAGS_INITIAL_PDU is still set, which means the initial + * iscsi_target_start_negotiation() is running, iscsi_target_do_login() + * via iscsi_target_sk_check_close() or iscsi_target_start_negotiation() + * via iscsi_target_sk_check_and_clear() is responsible for detecting the + * dropped TCP connection in iscsi_np process context, and cleaning up + * the remaining iscsi connection resources. + */ + if (state) { + pr_debug("iscsi_target_sk_state_change got failed state\n"); + set_bit(LOGIN_FLAGS_CLOSED, &conn->login_flags); + state = test_bit(LOGIN_FLAGS_INITIAL_PDU, &conn->login_flags); + write_unlock_bh(&sk->sk_callback_lock); - state = iscsi_target_sk_state_check(sk); - write_unlock_bh(&sk->sk_callback_lock); - - pr_debug("iscsi_target_sk_state_change: state: %d\n", state); + orig_state_change(sk); - if (!state) { - pr_debug("iscsi_target_sk_state_change got failed state\n"); - schedule_delayed_work(&conn->login_cleanup_work, 0); + if (!state) + schedule_delayed_work(&conn->login_work, 0); return; } + write_unlock_bh(&sk->sk_callback_lock); + orig_state_change(sk); } @@ -946,6 +1010,15 @@ static int iscsi_target_do_login(struct iscsi_conn *conn, struct iscsi_login *lo if (iscsi_target_handle_csg_one(conn, login) < 0) return -1; if (login_rsp->flags & ISCSI_FLAG_LOGIN_TRANSIT) { + /* + * Check to make sure the TCP connection has not + * dropped asynchronously while session reinstatement + * was occuring in this kthread context, before + * transitioning to full feature phase operation. + */ + if (iscsi_target_sk_check_close(conn)) + return -1; + login->tsih = conn->sess->tsih; login->login_complete = 1; iscsi_target_restore_sock_callbacks(conn); @@ -972,21 +1045,6 @@ static int iscsi_target_do_login(struct iscsi_conn *conn, struct iscsi_login *lo break; } - if (conn->sock) { - struct sock *sk = conn->sock->sk; - bool state; - - read_lock_bh(&sk->sk_callback_lock); - state = iscsi_target_sk_state_check(sk); - read_unlock_bh(&sk->sk_callback_lock); - - if (!state) { - pr_debug("iscsi_target_do_login() failed state for" - " conn: %p\n", conn); - return -1; - } - } - return 0; } @@ -1255,10 +1313,22 @@ int iscsi_target_start_negotiation( write_lock_bh(&sk->sk_callback_lock); set_bit(LOGIN_FLAGS_READY, &conn->login_flags); + set_bit(LOGIN_FLAGS_INITIAL_PDU, &conn->login_flags); write_unlock_bh(&sk->sk_callback_lock); } - + /* + * If iscsi_target_do_login returns zero to signal more PDU + * exchanges are required to complete the login, go ahead and + * clear LOGIN_FLAGS_INITIAL_PDU but only if the TCP connection + * is still active. + * + * Otherwise if TCP connection dropped asynchronously, go ahead + * and perform connection cleanup now. + */ ret = iscsi_target_do_login(conn, login); + if (!ret && iscsi_target_sk_check_and_clear(conn, LOGIN_FLAGS_INITIAL_PDU)) + ret = -1; + if (ret < 0) { cancel_delayed_work_sync(&conn->login_work); cancel_delayed_work_sync(&conn->login_cleanup_work); diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h index 275581d483dd..5f17fb770477 100644 --- a/include/target/iscsi/iscsi_target_core.h +++ b/include/target/iscsi/iscsi_target_core.h @@ -557,6 +557,7 @@ struct iscsi_conn { #define LOGIN_FLAGS_READ_ACTIVE 1 #define LOGIN_FLAGS_CLOSED 2 #define LOGIN_FLAGS_READY 4 +#define LOGIN_FLAGS_INITIAL_PDU 8 unsigned long login_flags; struct delayed_work login_work; struct delayed_work login_cleanup_work; -- 2.20.1