Hi Thomas,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[cannot apply to v5.4-rc7 next-20191111]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Thomas-Gleixner/x86-iopl-Prevent-user-space-from-using-CLI-STI-with-iopl-3/20191114-053418
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 004e8dce9c5595697951f7cd0e9f66b35c92265e
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

Note: the linux-review/Thomas-Gleixner/x86-iopl-Prevent-user-space-from-using-CLI-STI-with-iopl-3/20191114-053418 HEAD b14095464382fae4bf55028eb1cebe0e3cc1b9c8 builds fine.
      It only hurts bisectibility.

All errors (new ones prefixed by >>):

   arch/x86/kernel/ioport.c: In function 'ksys_ioperm':
>> arch/x86/kernel/ioport.c:83:7: error: 'struct tss_struct' has no member named 'io_bitmap_prev_max'; did you mean 'io_bitmap'?
     tss->io_bitmap_prev_max = bytes;
          ^~~~~~~~~~~~~~~~~~
          io_bitmap

vim +83 arch/x86/kernel/ioport.c

    15	
    16	/*
    17	 * this changes the io permissions bitmap in the current task.
    18	 */
    19	long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
    20	{
    21		unsigned int i, max_long, bytes, bytes_updated;
    22		struct thread_struct *t = &current->thread;
    23		struct tss_struct *tss;
    24		unsigned long *bitmap;
    25	
    26		if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
    27			return -EINVAL;
    28		if (turn_on && (!capable(CAP_SYS_RAWIO) ||
    29				security_locked_down(LOCKDOWN_IOPORT)))
    30			return -EPERM;
    31	
    32		/*
    33		 * If it's the first ioperm() call in this thread's lifetime, set the
    34		 * IO bitmap up. ioperm() is much less timing critical than clone(),
    35		 * this is why we delay this operation until now:
    36		 */
    37		bitmap = t->io_bitmap_ptr;
    38		if (!bitmap) {
    39			bitmap = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
    40			if (!bitmap)
    41				return -ENOMEM;
    42	
    43			memset(bitmap, 0xff, IO_BITMAP_BYTES);
    44		}
    45	
    46		/*
    47		 * Update the bitmap and the TSS copy with preemption disabled to
    48		 * prevent a race against context switch.
    49		 */
    50		preempt_disable();
    51		if (turn_on)
    52			bitmap_clear(bitmap, from, num);
    53		else
    54			bitmap_set(bitmap, from, num);
    55	
    56		/*
    57		 * Search for a (possibly new) maximum. This is simple and stupid,
    58		 * to keep it obviously correct:
    59		 */
    60		max_long = 0;
    61		for (i = 0; i < IO_BITMAP_LONGS; i++) {
    62			if (bitmap[i] != ~0UL)
    63				max_long = i;
    64		}
    65	
    66		bytes = (max_long + 1) * sizeof(unsigned long);
    67		bytes_updated = max(bytes, t->io_bitmap_max);
    68	
    69		/* Update the thread data */
    70		t->io_bitmap_max = bytes;
    71		/*
    72		 * Store the bitmap pointer (might be the same if the task already
    73		 * head one). Set the TIF flag, just in case this is the first
    74		 * invocation.
    75		 */
    76		t->io_bitmap_ptr = bitmap;
    77		set_thread_flag(TIF_IO_BITMAP);
    78	
    79		/* Update the TSS */
    80		tss = this_cpu_ptr(&cpu_tss_rw);
    81		memcpy(tss->io_bitmap, t->io_bitmap_ptr, bytes_updated);
    82		/* Store the new end of the zero bits */
  > 83		tss->io_bitmap_prev_max = bytes;
    84		/* Make sure the TSS limit covers the I/O bitmap. */
    85		refresh_tss_limit();
    86	
    87		preempt_enable();
    88	
    89		return 0;
    90	}
    91	

---
0-DAY kernel test infrastructure                 Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org Intel Corporation