Re: [PATCH] qedf: Added NULL pointer checks in qedf_update_link_speed().

From: Himanshu Madhani <himanshu.madhani@oracle.com>
To: Javed Hasan <jhasan@marvell.com>
Cc: Martin Petersen <martin.petersen@oracle.com>,
	linux-scsi <linux-scsi@vger.kernel.org>,
	"GR-QLogic-Storage-Upstream@marvell.com" 
	<GR-QLogic-Storage-Upstream@marvell.com>
Subject: Re: [PATCH] qedf: Added NULL pointer checks in qedf_update_link_speed().
Date: Wed, 12 May 2021 21:31:05 +0000	[thread overview]
Message-ID: <B932C218-C284-438D-9BE3-7FB60501E73C@oracle.com> (raw)
In-Reply-To: <20210512072533.23618-1-jhasan@marvell.com>

> On May 12, 2021, at 2:25 AM, Javed Hasan <jhasan@marvell.com> wrote:
> 
> Issue :- BUG: unable to handle kernel NULL pointer dereference at 000000000000003c
> On installation of RHEL-8.3.0-20200820.n.0 distro below stack
> was generating on error.
> 
> [   14.042059] Call Trace:
> [   14.042061]  <IRQ>
> [   14.042068]  qedf_link_update+0x144/0x1f0 [qedf]
> [   14.042117]  qed_link_update+0x5c/0x80 [qed]
> [   14.042135]  qed_mcp_handle_link_change+0x2d2/0x410 [qed]
> [   14.042155]  ? qed_set_ptt+0x70/0x80 [qed]
> [   14.042170]  ? qed_set_ptt+0x70/0x80 [qed]
> [   14.042186]  ? qed_rd+0x13/0x40 [qed]
> [   14.042205]  qed_mcp_handle_events+0x437/0x690 [qed]
> [   14.042221]  ? qed_set_ptt+0x70/0x80 [qed]
> [   14.042239]  qed_int_sp_dpc+0x3a6/0x3e0 [qed]
> [   14.042245]  tasklet_action_common.isra.14+0x5a/0x100
> [   14.042250]  __do_softirq+0xe4/0x2f8
> [   14.042253]  irq_exit+0xf7/0x100
> [   14.042255]  do_IRQ+0x7f/0xd0
> [   14.042257]  common_interrupt+0xf/0xf
> [   14.042259]  </IRQ>
> 
> Root cause :- API qedf_link_update() is getting called from QED.
>  but by that time shost_data is not initialised. That is leading NULL pointer dereference
>  when we try to derefference shost_data while updating supported_speeds.
> 
>  fc_host_supported_speeds(lport->host) = lport->link_supported_speeds;
> 
> Expansion of fc_host_supported_speeds.
> #define fc_host_supported_speeds(x)	\
>  (((struct fc_host_attrs *)(x)->shost_data)->supported_speeds)
> 
> Fix :- Added NULL pointer check for shost_data.
> 
> Signed-off-by: Javed Hasan <jhasan@marvell.com>
> 
> diff --git a/drivers/scsi/qedf/qedf_main.c b/drivers/scsi/qedf/qedf_main.c
> index 69f7784233f9..756231151882 100644
> --- a/drivers/scsi/qedf/qedf_main.c
> +++ b/drivers/scsi/qedf/qedf_main.c
> @@ -536,7 +536,9 @@ static void qedf_update_link_speed(struct qedf_ctx *qedf,
> 	if (linkmode_intersects(link->supported_caps, sup_caps))
> 		lport->link_supported_speeds |= FC_PORTSPEED_20GBIT;
> 
> -	fc_host_supported_speeds(lport->host) = lport->link_supported_speeds;
> +	if (lport->host && lport->host->shost_data)
> +		fc_host_supported_speeds(lport->host) =
> +			lport->link_supported_speeds;
> }
> 
> static void qedf_bw_update(void *dev)
> -- 
> 2.18.2
> 

This should be sent to stable with 

Fixes: 61d8658b4a435 ("scsi: qedf: Add QLogic FastLinQ offload FCoE driver framework.”)
Cc: <stable@vger.kernel.org>

With above added, Looks Good. 

Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>

--
Himanshu Madhani	 Oracle Linux Engineering