git: e0df0dce71d8 - main - powerpc_nvram: Fix a bug in the adler32 checksum.

The branch main has been updated by jhb:

URL: https://cgit.FreeBSD.org/src/commit/?id=e0df0dce71d86796195502b923243bb6bacdcdc2

commit e0df0dce71d86796195502b923243bb6bacdcdc2
Author:     John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2022-10-03 23:10:41 +0000
Commit:     John Baldwin <jhb@FreeBSD.org>
CommitDate: 2022-10-03 23:10:41 +0000

    powerpc_nvram: Fix a bug in the adler32 checksum.
    
    The Adler32 digest consists of two 16-bit words whose values are
    calculated modulo 65521 (largest prime < 2^16).  To avoid two division
    instructions per byte, this version copies an optimization found in
    zlib which defers the modulus until close to the point that the
    intermediate sums can overflow 2^32.  (zlib uses NMAX == 5552 for
    this, this version uses 5000)
    
    The bug is that in the deferred modulus case, the modulus was
    only applied to the high word (and twice at that) but not to
    the low word.  The fix is to apply it to both words.
    
    Reviewed by:    jhibbits
    Reported by:    Miod Vallat <miod@openbsd.org>
    Differential Revision:  https://reviews.freebsd.org/D36798
---
 sys/dev/powermac_nvram/powermac_nvram.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/dev/powermac_nvram/powermac_nvram.c b/sys/dev/powermac_nvram/powermac_nvram.c
index 247d35264441..e201a734ad1f 100644
--- a/sys/dev/powermac_nvram/powermac_nvram.c
+++ b/sys/dev/powermac_nvram/powermac_nvram.c
@@ -360,7 +360,7 @@ adler_checksum(uint8_t *data, int len)
 	high = 0;
 	for (i = 0; i < len; i++) {
 		if ((i % 5000) == 0) {
-			high %= 65521UL;
+			low %= 65521UL;
 			high %= 65521UL;
 		}
 		low += data[i];