scsi: qla2xxx: Fix double free of dsd_list during driver load

On driver load, scsi_add_host() can fail. This triggers the free path to
call qla2x00_mem_free() multiple times. This causes NULL pointer access of
ha->base_qpair. Add check before access.

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
 IP: [<ffffffffc118f73c>] qla2x00_mem_free+0x51c/0xcb0 [qla2xxx]
 PGD 8000001fcfe4a067 PUD 1fc8f0a067 PMD 0
 Oops: 0000 [#1] SMP
 RIP: 0010:[<ffffffffc118f73c>]  [<ffffffffc118f73c>] qla2x00_mem_free+0x51c/0xcb0 [qla2xxx]
 RSP: 0018:ffff8ace97a93a30  EFLAGS: 00010246
 RAX: 0000000000000000 RBX: ffff8ace8efd0000 RCX: 000000000000488f
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffff8ace97a93a60 R08: 000000000001f040 R09: ffffffff8678209b
 R10: ffff8acf7d6df040 R11: ffffc591c0fcc980 R12: ffffffff87034800
 R13: ffff8acf0e3cc740 R14: ffff8ace8efd0000 R15: 00000000fffffff4
 FS:  00007f4cf5449740(0000) GS:ffff8acf7d6c0000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000030 CR3: 0000001fc2f6c000 CR4: 00000000007607e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  [<ffffffff86781f18>] ? kobject_put+0x28/0x60
  [<ffffffffc119a59c>] qla2x00_probe_one+0x19fc/0x3040 [qla2xxx]

Fixes: efeda3b ("scsi: qla2xxx: Move resource to allow code reuse")
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Link: https://lore.kernel.org/r/20231016101749.5059-1-njavali@marvell.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Quinn Tran

drivers/scsi/qla2xxx/qla_os.c

@@ -4953,7 +4953,7 @@ qla2x00_mem_free(struct qla_hw_data *ha)
 	ha->gid_list = NULL;
 	ha->gid_list_dma = 0;
 
-	if (!list_empty(&ha->base_qpair->dsd_list)) {
+	if (ha->base_qpair && !list_empty(&ha->base_qpair->dsd_list)) {
 		struct dsd_dma *dsd_ptr, *tdsd_ptr;
 
 		/* clean up allocated prev pool */