[PATCH v2] ethtool: fix ethnl_bitmap32_not_zero() bit interval semantics

[PATCH v2] ethtool: fix ethnl_bitmap32_not_zero() bit interval semantics

[Chenguang Zhao]

ethnl_bitmap32_not_zero() should return true if some bit in [start, end)
is set:

- Fix inverted memchr_inv() sense: return true when the scan finds a
  non-zero byte, not when the middle words are all zero.
- Return false for an empty interval (end <= start).
- When end is 32-bit aligned, indices in [start, end) do not include any
  bits from map[end_word]; return false after earlier checks found no
  non-zero data.

Fixes: 10b518d4e6dd ("ethtool: netlink bitset handling")
Signed-off-by: Chenguang Zhao <zhaochenguang@kylinos.cn>
---
 v2:
  - Add Fixes tag as suggested by Leitao.
  - Fix other places in ethnl_bitmap32_not_zero()
    that are inconsistent with the documentation
    comments.
---
 net/ethtool/bitset.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ethtool/bitset.c b/net/ethtool/bitset.c
index 8bb98d3ea3db..14d3e68582c8 100644
--- a/net/ethtool/bitset.c
+++ b/net/ethtool/bitset.c
@@ -92,7 +92,7 @@ static bool ethnl_bitmap32_not_zero(const u32 *map, unsigned int start,
 	u32 mask;
 
 	if (end <= start)
-		return true;
+		return false;
 
 	if (start % 32) {
 		mask = ethnl_upper_bits(start);
@@ -105,11 +105,11 @@ static bool ethnl_bitmap32_not_zero(const u32 *map, unsigned int start,
 		start_word++;
 	}
 
-	if (!memchr_inv(map + start_word, '\0',
+	if (memchr_inv(map + start_word, '\0',
 			(end_word - start_word) * sizeof(u32)))
 		return true;
 	if (end % 32 == 0)
-		return true;
+		return false;
 	return map[end_word] & ethnl_lower_bits(end);
 }
 
-- 
2.25.1

Re: [PATCH v2] ethtool: fix ethnl_bitmap32_not_zero() bit interval semantics

[Jakub Kicinski]

On Sat,  9 May 2026 08:57:11 +0800 Chenguang Zhao wrote:
> -	if (!memchr_inv(map + start_word, '\0',
> +	if (memchr_inv(map + start_word, '\0',
>  			(end_word - start_word) * sizeof(u32)))

Please adjust the continuation line to match the opening bracket.
-- 
pw-bot: cr