| Message ID | 20221115125242.102344-1-mlombard@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [V3] target: fix a race condition between login_work and the login thread | expand |
út 15. 11. 2022 v 13:56 odesílatel Maurizio Lombardi <mlombard@redhat.com> napsal: > > > +/** > + * RETURN VALUE: > + * > + * 1 = Login successful > + * -1 = Login failed > + * 0 = More PDU exchanges required > + */ > static int iscsi_target_do_login(struct iscsit_conn *conn, struct iscsi_login *login) > { > int pdu_count = 0; > @@ -1363,12 +1370,13 @@ int iscsi_target_start_negotiation( > ret = -1; > > if (ret < 0) { > - cancel_delayed_work_sync(&conn->login_work); > iscsi_target_restore_sock_callbacks(conn); > iscsi_remove_failed_auth_entry(conn); > } > - if (ret != 0) > + if (ret != 0) { > + cancel_delayed_work_sync(&conn->login_work); > iscsi_target_nego_release(conn); > + } > > return ret; > } > If ret == 1 the login was successful, the socket callbacks have been restored by iscsi_target_do_login() so we just have to call cancel_delayed_work_sync() against login_work to fix the race condition. if ret == -1 the login was unsuccessful, I moved the cancel_delayed_work_sync() call from the (ret < 0) block to the (ret != 0) to close a potential race condition (we must restore the socket callbacks first). if ret == 0 then iscsi_target_do_login() clears LOGIN_FLAGS_INITIAL_PDU and passes the control to login_work. With this version of the patch, nothing has been changed in the login_work context so it should work exactly as before. iscsi_target_start_negotiation() is executed only in the login_thread context. Maurizio
diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c index f2919319ad38..fab92a460623 100644 --- a/drivers/target/iscsi/iscsi_target_nego.c +++ b/drivers/target/iscsi/iscsi_target_nego.c @@ -1018,6 +1018,13 @@ static int iscsi_target_handle_csg_one(struct iscsit_conn *conn, struct iscsi_lo return 0; } +/** + * RETURN VALUE: + * + * 1 = Login successful + * -1 = Login failed + * 0 = More PDU exchanges required + */ static int iscsi_target_do_login(struct iscsit_conn *conn, struct iscsi_login *login) { int pdu_count = 0; @@ -1363,12 +1370,13 @@ int iscsi_target_start_negotiation( ret = -1; if (ret < 0) { - cancel_delayed_work_sync(&conn->login_work); iscsi_target_restore_sock_callbacks(conn); iscsi_remove_failed_auth_entry(conn); } - if (ret != 0) + if (ret != 0) { + cancel_delayed_work_sync(&conn->login_work); iscsi_target_nego_release(conn); + } return ret; }
In case a malicious initiator sends some random data immediately after a login PDU; the iscsi_target_sk_data_ready() callback will schedule the login_work and, at the same time, the negotiation may end without clearing the LOGIN_FLAGS_INITIAL_PDU flag (because no additional PDU exchanges are required to complete the login). The login has been completed but the login_work function will find the LOGIN_FLAGS_INITIAL_PDU flag set and will never stop from rescheduling itself; at this point, if the initiator drops the connection, the iscsit_conn structure will be freed, login_work will dereference a released socket structure and the kernel crashes. BUG: kernel NULL pointer dereference, address: 0000000000000230 PF: supervisor write access in kernel mode PF: error_code(0x0002) - not-present page Workqueue: events iscsi_target_do_login_rx [iscsi_target_mod] RIP: 0010:_raw_read_lock_bh+0x15/0x30 Call trace: iscsi_target_do_login_rx+0x75/0x3f0 [iscsi_target_mod] process_one_work+0x1e8/0x3c0 Fix this bug by forcing login_work to stop after the login has been completed and the socket callbacks have been restored. Add a comment to clearify the return values of iscsi_target_do_login() v3: cancel_delayed_work_sync() should be called by iscsi_target_start_negotiation(), because the latter is only executed in login_thread context V2: remove an unnecessary call to cancel_delayed_work(); fix a potential race condition in iscsi_start_negotiation() and in iscsi_target_do_login_rx()'s error paths Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> --- drivers/target/iscsi/iscsi_target_nego.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)