Re: [PATCH 7/7] scsi: target: Fix multiple LUN_RESET handling

[Dmitry Bogdanov <d.bogdanov@yadro.com>]

On Wed, Dec 07, 2022 at 09:10:02PM -0600, Mike Christie wrote:
> 
> This fixes a bug where an initiator thinks a LUN_RESET has cleaned
> up running commands when it hasn't. The bug was added in:
> 
> commit 51ec502a3266 ("target: Delete tmr from list before processing")
> 
> The problem occurs when:
> 
> 1. We have N IO cmds running in the target layer spread over 2 sessions.
> 2. The initiator sends a LUN_RESET for each session.
> 3. session1's LUN_RESET loops over all the running commands from both
> sessions and moves them to its local drain_task_list.
> 4. session2's LUN_RESET does not see the LUN_RESET from session1 because
> the commit above has it remove itself. session2 also does not see any
> commands since the other reset moved them off the state lists.
> 5. sessions2's LUN_RESET will then complete with a successful response.
> 6. sessions2's inititor believes the running commands on its session are
> now cleaned up due to the successful response and cleans up the running
> commands from its side. It then restarts them.
> 7. The commands do eventually complete on the backend and the target
> starts to return aborted task statuses for them. The initiator will
> either throw a invalid ITT error or might accidentally lookup a new task
> if the ITT has been reallocated already.
> 
> This fixes the bug by reverting the patch.
> 
> Fixes: 51ec502a3266 ("target: Delete tmr from list before processing")
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>  drivers/target/target_core_tmr.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
> index bac111456fa1..ba2a2c18dae9 100644
> --- a/drivers/target/target_core_tmr.c
> +++ b/drivers/target/target_core_tmr.c
> @@ -188,9 +188,10 @@ static void core_tmr_drain_tmr_list(
>          * LUN_RESET tmr..
>          */
>         spin_lock_irqsave(&dev->se_tmr_lock, flags);
> -       if (tmr)
> -               list_del_init(&tmr->tmr_list);
>         list_for_each_entry_safe(tmr_p, tmr_pp, &dev->dev_tmr_list, tmr_list) {
> +               if (tmr_p == tmr)
> +                       continue;
> +
>                 cmd = tmr_p->task_cmd;
>                 if (!cmd) {
>                         pr_err("Unable to locate struct se_cmd for TMR\n");
> --
> 2.25.1
> 

Reviewed-by: Dmitry Bogdanov <d.bogdanov@yadro.com>