linux-kernel - Re: [PATCH v2] scsi: hisi_sas: Fix NULL pointer dereference

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Date:   Fri, 19 Oct 2018 08:54:04 +0800
From:   "chenxiang (M)" <chenxiang66@...ilicon.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        John Garry <john.garry@...wei.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] scsi: hisi_sas: Fix NULL pointer dereference

在 2018/10/19 0:59, Gustavo A. R. Silva 写道:
> There is a NULL pointer dereference in case *slot* happens to
> be NULL at lines 1053 and 1878:
>
> struct hisi_sas_cq *cq =
> 	&hisi_hba->cq[slot->dlvry_queue];
>
> Notice that *slot* is being NULL checked at lines 1057 and 1881:
> if (slot), which implies it may be NULL.
>
> Fix this by placing the declaration and definition of variable cq,
> which contains the pointer dereference slot->dlvry_queue, after
> slot has been properly NULL checked.
>
> Addresses-Coverity-ID: 1474515 ("Dereference before null check")
> Addresses-Coverity-ID: 1474520 ("Dereference before null check")
> Fixes: 584f53fe5f52 ("scsi: hisi_sas: Fix the race between IO completion and timeout for SMP/internal IO")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Xiang Chen <chenxiang66@...ilicon.com>
Thanks!

> ---
> Changes in v2:
>   - Fix another instance of the same issue at line 1053.
>   - Update commit log.
>
>   drivers/scsi/hisi_sas/hisi_sas_main.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
> index 2e5eaf1..b3f01d5 100644
> --- a/drivers/scsi/hisi_sas/hisi_sas_main.c
> +++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
> @@ -1050,11 +1050,11 @@ static int hisi_sas_exec_internal_tmf_task(struct domain_device *device,
>   		if ((task->task_state_flags & SAS_TASK_STATE_ABORTED)) {
>   			if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) {
>   				struct hisi_sas_slot *slot = task->lldd_task;
> -				struct hisi_sas_cq *cq =
> -					&hisi_hba->cq[slot->dlvry_queue];
>   
>   				dev_err(dev, "abort tmf: TMF task timeout and not done\n");
>   				if (slot) {
> +					struct hisi_sas_cq *cq =
> +					       &hisi_hba->cq[slot->dlvry_queue];
>   					/*
>   					 * flush tasklet to avoid free'ing task
>   					 * before using task in IO completion
> @@ -1875,10 +1875,10 @@ hisi_sas_internal_task_abort(struct hisi_hba *hisi_hba,
>   	if ((task->task_state_flags & SAS_TASK_STATE_ABORTED)) {
>   		if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) {
>   			struct hisi_sas_slot *slot = task->lldd_task;
> -			struct hisi_sas_cq *cq =
> -				&hisi_hba->cq[slot->dlvry_queue];
>   
>   			if (slot) {
> +				struct hisi_sas_cq *cq =
> +					&hisi_hba->cq[slot->dlvry_queue];
>   				/*
>   				 * flush tasklet to avoid free'ing task
>   				 * before using task in IO completion