scsi: qla2xxx: Fix double free bug after firmware timeout

This patch is based on Max's original patch.

When the qla2xxx firmware is unavailable, eventually
qla2x00_sp_timeout() is reached, which calls the timeout function and
frees the srb_t instance.

The timeout function always resolves to qla2x00_async_iocb_timeout(),
which invokes another callback function called "done".  All of these
qla2x00_*_sp_done() callbacks also free the srb_t instance; after
returning to qla2x00_sp_timeout(), it is freed again.

The fix is to remove the "sp->free(sp)" call from qla2x00_sp_timeout()
and add it to those code paths in qla2x00_async_iocb_timeout() which
do not already free the object.

This is how it looks like with KASAN:

BUG: KASAN: use-after-free in qla2x00_sp_timeout+0x228/0x250
Read of size 8 at addr ffff88278147a590 by task swapper/2/0

Allocated by task 1502:
save_stack+0x33/0xa0
kasan_kmalloc+0xa0/0xd0
kmem_cache_alloc+0xb8/0x1c0
mempool_alloc+0xd6/0x260
qla24xx_async_gnl+0x3c5/0x1100

Freed by task 0:
save_stack+0x33/0xa0
kasan_slab_free+0x72/0xc0
kmem_cache_free+0x75/0x200
qla24xx_async_gnl_sp_done+0x556/0x9e0
qla2x00_async_iocb_timeout+0x1c7/0x420
qla2x00_sp_timeout+0x16d/0x250
call_timer_fn+0x36/0x200

The buggy address belongs to the object at ffff88278147a440
which belongs to the cache qla2xxx_srbs of size 344
The buggy address is located 336 bytes inside of
344-byte region [ffff88278147a440, ffff88278147a598)

Reported-by: Max Kellermann <mk@cm4all.com>
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Cc: Max Kellermann <mk@cm4all.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qla2xxx/qla_init.c

@@ -59,8 +59,6 @@ qla2x00_sp_timeout(struct timer_list *t)
 	req->outstanding_cmds[sp->handle] = NULL;
 	iocb = &sp->u.iocb_cmd;
 	iocb->timeout(sp);
-	if (sp->type != SRB_ELS_DCMD)
-		sp->free(sp);
 	spin_unlock_irqrestore(&vha->hw->hardware_lock, flags);
 }
 
@@ -102,7 +100,6 @@ qla2x00_async_iocb_timeout(void *data)
 	srb_t *sp = data;
 	fc_port_t *fcport = sp->fcport;
 	struct srb_iocb *lio = &sp->u.iocb_cmd;
-	struct event_arg ea;
 
 	if (fcport) {
 		ql_dbg(ql_dbg_disc, fcport->vha, 0x2071,
@@ -117,25 +114,13 @@ qla2x00_async_iocb_timeout(void *data)
 
 	switch (sp->type) {
 	case SRB_LOGIN_CMD:
-		if (!fcport)
-			break;
 		/* Retry as needed. */
 		lio->u.logio.data[0] = MBS_COMMAND_ERROR;
 		lio->u.logio.data[1] = lio->u.logio.flags & SRB_LOGIN_RETRIED ?
 			QLA_LOGIO_LOGIN_RETRIED : 0;
-		memset(&ea, 0, sizeof(ea));
-		ea.event = FCME_PLOGI_DONE;
-		ea.fcport = sp->fcport;
-		ea.data[0] = lio->u.logio.data[0];
-		ea.data[1] = lio->u.logio.data[1];
-		ea.sp = sp;
-		qla24xx_handle_plogi_done_event(fcport->vha, &ea);
+		sp->done(sp, QLA_FUNCTION_TIMEOUT);
 		break;
 	case SRB_LOGOUT_CMD:
-		if (!fcport)
-			break;
-		qlt_logo_completion_handler(fcport, QLA_FUNCTION_TIMEOUT);
-		break;
 	case SRB_CT_PTHRU_CMD:
 	case SRB_MB_IOCB:
 	case SRB_NACK_PLOGI:
@@ -235,12 +220,10 @@ static void
 qla2x00_async_logout_sp_done(void *ptr, int res)
 {
 	srb_t *sp = ptr;
-	struct srb_iocb *lio = &sp->u.iocb_cmd;
 
 	sp->fcport->flags &= ~(FCF_ASYNC_SENT | FCF_ASYNC_ACTIVE);
-	if (!test_bit(UNLOADING, &sp->vha->dpc_flags))
-		qla2x00_post_async_logout_done_work(sp->vha, sp->fcport,
-		    lio->u.logio.data);
+	sp->fcport->login_gen++;
+	qlt_logo_completion_handler(sp->fcport, res);
 	sp->free(sp);
 }