In `ni_find_route_source()`, `tables->route_values` gets dereferenced. However it is possible that `tables->route_values` is `NULL`, leading to a null pointer dereference. `tables->route_values` will be `NULL` if the call to `ni_assign_device_routes()` during board initialization returned an error due to missing device family routing information or missing board-specific routing information. For example, there is currently no board-specific routing information provided for the PCIe-6251 board and several other boards, so those are affected by this bug.

The bug is triggered when `ni_find_route_source()` is called via `ni_check_trigger_arg()` or `ni_check_trigger_arg_roffs()` when checking the arguments for setting up asynchronous commands. Fix it by returning `-EINVAL` if `tables->route_values` is `NULL`.

Even with this fix, setting up asynchronous commands to use external trigger sources for boards with missing routing information will still fail gracefully. Since `ni_find_route_source()` only depends on the device family routing information, it would be better if that was made available even if the board-specific routing information is missing. That will be addressed by another patch.

Fixes: 4bb90c87abbe ("staging: comedi: add interface to ni routing table information") Cc: stable@vger.kernel.org # 4.20+ Cc: Spencer E. Olson olsonse@umich.edu Signed-off-by: Ian Abbott abbotti@mev.co.uk --- drivers/staging/comedi/drivers/ni_routes.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/comedi/drivers/ni_routes.c b/drivers/staging/comedi/drivers/ni_routes.c index 673d732dcb8f..9627bd1d2a78 100644 --- a/drivers/staging/comedi/drivers/ni_routes.c +++ b/drivers/staging/comedi/drivers/ni_routes.c @@ -487,6 +487,9 @@ int ni_find_route_source(const u8 src_sel_reg_value, int dest, { int src;

+ if (!tables->route_values) + return -EINVAL; + dest = B(dest); /* subtract NI names offset */ /* ensure we are not going to under/over run the route value table */ if (dest < 0 || dest >= NI_NUM_NAMES)