Re: [syzbot] [kernel?] general protection fault in pcl818_ai_cancel

[Hillf Danton <hdanton@sina.com>]

> Date: Sat, 05 Jul 2025 03:41:26 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    26ffb3d6f02c Add linux-next specific files for 20250704
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1304cf70580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8c567bd5a036e49d
> dashboard link: https://syzkaller.appspot.com/bug?extid=fce5d9d5bd067d6fbe9b
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11022c8c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1704cf70580000

#syz test

--- x/drivers/comedi/drivers/pcl818.c
+++ y/drivers/comedi/drivers/pcl818.c
@@ -759,12 +759,15 @@ static int pcl818_ai_cancel(struct comed
 {
 	struct pcl818_private *devpriv = dev->private;
 	struct comedi_isadma *dma = devpriv->dma;
-	struct comedi_cmd *cmd = &s->async->cmd;
 
 	if (!devpriv->ai_cmd_running)
 		return 0;
 
 	if (dma) {
+		struct comedi_cmd *cmd;
+		if (!s || !s->async)
+			return 0;
+		cmd = &s->async->cmd;
 		if (cmd->stop_src == TRIG_NONE ||
 		    (cmd->stop_src == TRIG_COUNT &&
 		     s->async->scans_done < cmd->stop_arg)) {
--