Re: [PATCH 06/21] can: netlink: add can_validate_databittiming()

[kernel test robot <lkp@intel.com>]

Hi Vincent,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3]

url:    https://github.com/intel-lab-lkp/linux/commits/Vincent-Mailhol/can-dev-move-struct-data_bittiming_params-to-linux-can-bittiming-h/20250903-170807
base:   2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
patch link:    https://lore.kernel.org/r/20250903-canxl-netlink-prep-v1-6-904bd6037cd9%40kernel.org
patch subject: [PATCH 06/21] can: netlink: add can_validate_databittiming()
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509050259.NjPdQyAD-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/net/can/dev/netlink.c:111:6: warning: variable 'is_on' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/can/dev/netlink.c:119:6: note: uninitialized use occurs here
     119 |         if (is_on) {
         |             ^~~~~
   drivers/net/can/dev/netlink.c:111:2: note: remove the 'if' if its condition is always true
     111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     112 |                 data_tdc = data[IFLA_CAN_TDC];
     113 |                 tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
     114 |                 is_on = flags & CAN_CTRLMODE_FD;
     115 |         } else {
         |           ~~~~~~
     116 |                 WARN_ON(1); /* Place holder for CAN XL */
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     117 |         }
         |         ~
   drivers/net/can/dev/netlink.c:108:12: note: initialize the variable 'is_on' to silence this warning
     108 |         bool is_on;
         |                   ^
         |                    = 0
   1 warning generated.


vim +111 drivers/net/can/dev/netlink.c

   101	
   102	static int can_validate_databittiming(struct nlattr *data[],
   103					      struct netlink_ext_ack *extack,
   104					      int ifla_can_data_bittiming, u32 flags)
   105	{
   106		struct nlattr *data_tdc;
   107		u32 tdc_flags;
   108		bool is_on;
   109		int err;
   110	
 > 111		if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
   112			data_tdc = data[IFLA_CAN_TDC];
   113			tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
   114			is_on = flags & CAN_CTRLMODE_FD;
   115		} else {
   116			WARN_ON(1); /* Place holder for CAN XL */
   117		}
   118	
   119		if (is_on) {
   120			if (!data[IFLA_CAN_BITTIMING] || !data[ifla_can_data_bittiming])
   121				return -EOPNOTSUPP;
   122		}
   123	
   124		if (data[ifla_can_data_bittiming] || data_tdc) {
   125			if (!is_on)
   126				return -EOPNOTSUPP;
   127		}
   128	
   129		err = can_validate_bittiming(data, extack, ifla_can_data_bittiming);
   130		if (err)
   131			return err;
   132	
   133		err = can_validate_tdc(data_tdc, extack, tdc_flags);
   134		if (err)
   135			return err;
   136	
   137		return 0;
   138	}
   139	

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