Re: [PATCH v3 05/14] scsi: target: iscsit: stop/wait on cmds during conn close

[Maurizio Lombardi <mlombard@redhat.com>]

po 30. 1. 2023 v 0:45 odesílatel Mike Christie
<michael.christie@oracle.com> napsal:
>
> This fixes a bug added in:
>
> commit f36199355c64 ("scsi: target: iscsi: Fix cmd abort fabric stop
> race")
>
> If we have multiple sessions to the same se_device we can hit a race where
> a LUN_RESET on one session cleans up the se_cmds from under another
> session which is being closed. This results in the closing session freeing
> its conn/session structs while they are still in use.
>
> The bug is:
>
> 1. Session1 has IO se_cmd1.
> 2. Session2 can also have se_cmds for IO and optionally TMRs for ABORTS
> but then gets a LUN_RESET.
> 3. The LUN_RESET on session2 sees the se_cmds on session1 and during
> the drain stages marks them all with CMD_T_ABORTED.
> 4. session1 is now closed so iscsit_release_commands_from_conn only sees
> se_cmds with the CMD_T_ABORTED bit set and returns immediately even
> though we have outstanding commands.
> 5. session1's connection and session are freed.
> 6. The backend request for se_cmd1 completes and it accesses the freed
> connection/session.
>
> This hooks the iscsit layer into the cmd counter code, so we can wait for
> all outstanding se_cmds before freeing the connection.
>
> Fixes: f36199355c64 ("scsi: target: iscsi: Fix cmd abort fabric stop race")
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>  drivers/target/iscsi/iscsi_target.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
> index 11115c207844..83b007141229 100644
> --- a/drivers/target/iscsi/iscsi_target.c
> +++ b/drivers/target/iscsi/iscsi_target.c
> @@ -4245,6 +4245,16 @@ static void iscsit_release_commands_from_conn(struct iscsit_conn *conn)
>                 iscsit_free_cmd(cmd, true);
>
>         }
> +
> +       /*
> +        * Wait on commands that were cleaned up via the aborted_task path.
> +        * LLDs that implement iscsit_wait_conn will already have waited for
> +        * commands.
> +        */
> +       if (!conn->conn_transport->iscsit_wait_conn) {
> +               target_stop_cmd_counter(conn->cmd_cnt);
> +               target_wait_for_cmds(conn->cmd_cnt);
> +       }
>  }
>
>  static void iscsit_stop_timers_for_cmds(
> --
> 2.25.1
>

Reviewed-by: Maurizio Lombardi <mlombard@redhat.com>