From 6cab7a37f5c048bb2a768f24b0ec748b052fda09 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Wed, 8 Oct 2014 16:09:14 +0100 Subject: staging: comedi: (regression) channel list must be set for COMEDI_CMD ioctl `do_cmd_ioctl()`, the handler for the `COMEDI_CMD` ioctl can incorrectly call the Comedi subdevice's `do_cmd()` handler with a NULL channel list pointer. This is a regression as the `do_cmd()` handler has never been expected to deal with that, leading to a kernel OOPS when it tries to dereference it. A NULL channel list pointer is allowed for the `COMEDI_CMDTEST` ioctl, handled by `do_cmdtest_ioctl()` and the subdevice's `do_cmdtest()` handler, but not for the `COMEDI_CMD` ioctl and its handlers. Both `do_cmd_ioctl()` and `do_cmdtest_ioctl()` call `__comedi_get_user_chanlist()` to copy the channel list from user memory into dynamically allocated kernel memory and check it for consistency. That function currently returns 0 if the `user_chanlist` parameter (pointing to the channel list in user memory) is NULL. That's fine for `do_cmdtest_ioctl()`, but `do_cmd_ioctl()` incorrectly assumes the kernel copy of the channel list has been set-up correctly. Fix it by not allowing the `user_chanlist` parameter to be NULL in `__comedi_get_user_chanlist()`, and only calling it from `do_cmdtest_ioctl()` if the parameter is non-NULL. Thanks to Bernd Porr for reporting the bug via an initial patch sent privately. Fixes: c6cd0eefb27b ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()") Reported-by: Bernd Porr Signed-off-by: Ian Abbott Reviewed-by: H Hartley Sweeten Cc: Bernd Porr Cc: # 3.15.y 3.16.y 3.17.y Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'drivers/staging') diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 495969f46e76..a9b7fe52d380 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1462,10 +1462,6 @@ static int __comedi_get_user_chanlist(struct comedi_device *dev, unsigned int *chanlist; int ret; - /* user_chanlist could be NULL for do_cmdtest ioctls */ - if (!user_chanlist) - return 0; - chanlist = memdup_user(user_chanlist, cmd->chanlist_len * sizeof(unsigned int)); if (IS_ERR(chanlist)) @@ -1609,10 +1605,13 @@ static int do_cmdtest_ioctl(struct comedi_device *dev, s = &dev->subdevices[cmd.subdev]; - /* load channel/gain list */ - ret = __comedi_get_user_chanlist(dev, s, user_chanlist, &cmd); - if (ret) - return ret; + /* user_chanlist can be NULL for COMEDI_CMDTEST ioctl */ + if (user_chanlist) { + /* load channel/gain list */ + ret = __comedi_get_user_chanlist(dev, s, user_chanlist, &cmd); + if (ret) + return ret; + } ret = s->do_cmdtest(dev, s, &cmd); -- cgit v1.2.3-55-g7522