scsi: qedi: Check targetname while finding boot target information

The kernel panic was observed during iSCSI discovery via offload with below
call trace,

[ 2115.646901] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 2115.646909] IP: [<ffffffffacf7f0cc>] strncmp+0xc/0x60
[ 2115.646927] PGD 0
[ 2115.646932] Oops: 0000 [#1] SMP
[ 2115.647107] CPU: 24 PID: 264 Comm: kworker/24:1 Kdump: loaded Tainted: G
               OE  ------------   3.10.0-957.el7.x86_64 #1
[ 2115.647133] Workqueue: slowpath-13:00. qed_slowpath_task [qed]
[ 2115.647135] task: ffff8d66af80b0c0 ti: ffff8d66afb80000 task.ti: ffff8d66afb80000
[ 2115.647136] RIP: 0010:[<ffffffffacf7f0cc>]  [<ffffffffacf7f0cc>] strncmp+0xc/0x60
[ 2115.647141] RSP: 0018:ffff8d66afb83c68  EFLAGS: 00010206
[ 2115.647143] RAX: 0000000000000001 RBX: 0000000000000007 RCX: 000000000000000a
[ 2115.647144] RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8d632b3ba040
[ 2115.647145] RBP: ffff8d66afb83c68 R08: 0000000000000000 R09: 000000000000ffff
[ 2115.647147] R10: 0000000000000007 R11: 0000000000000800 R12: ffff8d66a30007a0
[ 2115.647148] R13: ffff8d66747a3c10 R14: ffff8d632b3ba000 R15: ffff8d66747a32f8
[ 2115.647149] FS:  0000000000000000(0000) GS:ffff8d66aff00000(0000) knlGS:0000000000000000
[ 2115.647151] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2115.647152] CR2: 0000000000000000 CR3: 0000000509610000 CR4: 00000000007607e0
[ 2115.647153] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2115.647154] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2115.647155] PKRU: 00000000
[ 2115.647157] Call Trace:
[ 2115.647165]  [<ffffffffc0634cc5>] qedi_get_protocol_tlv_data+0x2c5/0x510 [qedi]
[ 2115.647184]  [<ffffffffc05968f5>] ? qed_mfw_process_tlv_req+0x245/0xbe0 [qed]
[ 2115.647195]  [<ffffffffc05496cb>] qed_mfw_fill_tlv_data+0x4b/0xb0 [qed]
[ 2115.647206]  [<ffffffffc0596911>] qed_mfw_process_tlv_req+0x261/0xbe0 [qed]
[ 2115.647215]  [<ffffffffacce0e8e>] ? dequeue_task_fair+0x41e/0x660
[ 2115.647221]  [<ffffffffacc2a59e>] ? __switch_to+0xce/0x580
[ 2115.647230]  [<ffffffffc0546013>] qed_slowpath_task+0xa3/0x160 [qed]
[ 2115.647278] RIP  [<ffffffffacf7f0cc>] strncmp+0xc/0x60

Fix kernel panic by validating the session targetname before providing TLV
data and confirming the presence of boot targets.
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qedi/qedi_main.c

@@ -990,6 +990,9 @@ static int qedi_find_boot_info(struct qedi_ctx *qedi,
 		if (!iscsi_is_session_online(cls_sess))
 			continue;
 
+		if (!sess->targetname)
+			continue;
+
 		if (pri_ctrl_flags) {
 			if (!strcmp(pri_tgt->iscsi_name, sess->targetname) &&
 			    !strcmp(pri_tgt->ip_addr, ep_ip_addr)) {