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

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 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@xxxxxxxxxxx>

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




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