Prevent dereference of NULL chanlist pointer in ai cmdtest leading to

kernel Oops.

diff --git a/comedi/drivers/ni_labpc.c b/comedi/drivers/ni_labpc.c
index f9afdc8afcaaca44b8343fe9a6ad571281a2355a..d5baf94eed58d35da5ff3d06edc2021360fef9ef 100644 (file)
--- a/comedi/drivers/ni_labpc.c
+++ b/comedi/drivers/ni_labpc.c
@@ -783,6 +783,10 @@ static enum scan_mode labpc_ai_scan_mode(const comedi_cmd * cmd)
        if (cmd->chanlist_len == 1)
                return MODE_SINGLE_CHAN;
 
+       /* chanlist may be NULL during cmdtest. */
+       if (cmd->chanlist == NULL)
+               return MODE_MULT_CHAN_UP;
+
        if (CR_CHAN(cmd->chanlist[0]) == CR_CHAN(cmd->chanlist[1]))
                return MODE_SINGLE_CHAN_INTERVAL;