Add the __counted_by compiler attribute to the flexible array member
range to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Compile-tested only.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 include/linux/hyperv.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 22c22fb91042..ec62d625c439 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -643,7 +643,7 @@ struct vmbus_channel_gpadl_header {
 	u32 gpadl;
 	u16 range_buflen;
 	u16 rangecount;
-	struct gpa_range range[];
+	struct gpa_range range[] __counted_by(rangecount);
 } __packed;
 
 /* This is the followup packet that contains more PFNs. */
-- 
2.47.0

Hi Thorsten,

kernel test robot noticed the following build warnings:

[auto build test WARNING on kees/for-next/pstore]
[also build test WARNING on kees/for-next/kspp linus/master v6.12-rc3 next-20241015]
[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/Thorsten-Blum/hv-hyperv-h-Annotate-vmbus_channel_gpadl_header-with-__counted_by/20241015-182055
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/pstore
patch link:    https://lore.kernel.org/r/20241015101829.94876-2-thorsten.blum%40linux.dev
patch subject: [PATCH] hv: hyperv.h: Annotate vmbus_channel_gpadl_header with __counted_by()
config: arm64-randconfig-001-20241016 (https://download.01.org/0day-ci/archive/20241016/202410161148.ODpoEJF0-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project bfe84f7085d82d06d61c632a7bad1e692fd159e4)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241016/202410161148.ODpoEJF0-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/202410161148.ODpoEJF0-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from arch/arm64/hyperv/hv_core.c:13:
   In file included from include/linux/mm.h:2228:
   include/linux/vmstat.h:500:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     500 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     501 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:507:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     507 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     508 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:514:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     514 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:519:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     519 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     520 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:528:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     528 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     529 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   In file included from arch/arm64/hyperv/hv_core.c:14:
>> include/linux/hyperv.h:646:2: warning: 'counted_by' should not be applied to an array with element of unknown size because 'struct gpa_range' is a struct type with a flexible array member. This will be an error in a future compiler version [-Wbounds-safety-counted-by-elt-type-unknown-size]
     646 |         struct gpa_range range[] __counted_by(rangecount);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~
   6 warnings generated.


vim +646 include/linux/hyperv.h

   633	
   634	/*
   635	 * The number of PFNs in a GPADL message is defined by the number of
   636	 * pages that would be spanned by ByteCount and ByteOffset.  If the
   637	 * implied number of PFNs won't fit in this packet, there will be a
   638	 * follow-up packet that contains more.
   639	 */
   640	struct vmbus_channel_gpadl_header {
   641		struct vmbus_channel_message_header header;
   642		u32 child_relid;
   643		u32 gpadl;
   644		u16 range_buflen;
   645		u16 rangecount;
 > 646		struct gpa_range range[] __counted_by(rangecount);
   647	} __packed;
   648	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki