Re: [PATCH v2] tty: n_tty: use kvzalloc/kvfree for line discipline data

Hi Xin,

kernel test robot noticed the following build errors:

[auto build test ERROR on tty/tty-testing]
[also build test ERROR on tty/tty-next tty/tty-linus linus/master v7.2 next-20260819]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Xin-Chen/tty-n_tty-use-kvzalloc-kvfree-for-line-discipline-data/20260818-150324
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link:    https://lore.kernel.org/r/20260818070324.136726-1-xin.chen2%40oss.qualcomm.com
patch subject: [PATCH v2] tty: n_tty: use kvzalloc/kvfree for line discipline data
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260821/[email protected]/config)
compiler: clang version 22.1.3 (https://github.com/llvm/llvm-project e9846648fd6183ee6d8cbdb4502213fcf902a211)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260821/[email protected]/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 <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All errors (new ones prefixed by >>):

>> drivers/tty/n_tty.c:1890:8: error: incompatible pointer types assigning to 'struct n_tty_data *' from 'typeof (ldata) *' (aka 'struct n_tty_data **'); dereference with * [-Wincompatible-pointer-types]
    1890 |         ldata = kvzalloc_obj(ldata);
         |               ^ ~~~~~~~~~~~~~~~~~~~
         |                 *(                 )
   1 error generated.


vim +1890 drivers/tty/n_tty.c

  1876	
  1877	/**
  1878	 * n_tty_open		-	open an ldisc
  1879	 * @tty: terminal to open
  1880	 *
  1881	 * Called when this line discipline is being attached to the terminal device.
  1882	 * Can sleep. Called serialized so that no other events will occur in parallel.
  1883	 * No further open will occur until a close.
  1884	 */
  1885	static int n_tty_open(struct tty_struct *tty)
  1886	{
  1887		struct n_tty_data *ldata;
  1888	
  1889		/* Currently a malloc failure here can panic */
> 1890		ldata = kvzalloc_obj(ldata);
  1891		if (!ldata)
  1892			return -ENOMEM;
  1893	
  1894		ldata->overrun_time = jiffies;
  1895		mutex_init(&ldata->atomic_read_lock);
  1896		mutex_init(&ldata->output_lock);
  1897	
  1898		tty->disc_data = ldata;
  1899		tty->closing = 0;
  1900		/* indicate buffer work may resume */
  1901		clear_bit(TTY_LDISC_HALTED, &tty->flags);
  1902		n_tty_set_termios(tty, NULL);
  1903		tty_unthrottle(tty);
  1904		return 0;
  1905	}
  1906	

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