From c04cffb8c51618538f0c05c478a931eb6e1a806b Mon Sep 17 00:00:00 2001
From: Bradley Morgan <include@grrlz.net>
Date: Sun, 21 Jun 2026 12:11:33 +0000
Subject: [PATCH] lib/string: fix memchr_inv() for large ranges

memchr_inv() takes a size_t length but counts 8 byte words in an unsigned
int.  At 32GiB that count wraps, so the scan can quietly miss most of the
range.

Use size_t for the word count.

Link: https://lore.kernel.org/20260621121133.16460-1-include@grrlz.net
Fixes: 798248206b59 ("lib/string.c: introduce memchr_inv()")
Signed-off-by: Bradley Morgan <include@grrlz.net>
Cc: Akinbou Mita <akinobu.mita@gmail.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Christoph Lameer <cl@linux-foundation.org>
Cc: Joern Engel <joern@logfs.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 lib/string.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/string.c b/lib/string.c
index a4e8ad23577d..a3778d5aab4a 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -821,7 +821,8 @@ void *memchr_inv(const void *start, int c, size_t bytes)
 {
 	u8 value = c;
 	u64 value64;
-	unsigned int words, prefix;
+	size_t words;
+	unsigned int prefix;
 
 	if (bytes <= 16)
 		return check_bytes8(start, value, bytes);