git: 44c1914ee672 - stable/13 - powerpc_nvram: Fix a bug in the adler32 checksum.

The branch stable/13 has been updated by jhb:

URL: https://cgit.FreeBSD.org/src/commit/?id=44c1914ee672487fe19363647f787958f2e3bebb

commit 44c1914ee672487fe19363647f787958f2e3bebb
Author:     John Baldwin <jhb@FreeBSD.org>
AuthorDate: 2022-10-03 23:10:41 +0000
Commit:     John Baldwin <jhb@FreeBSD.org>
CommitDate: 2022-11-11 18:18:53 +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
    
    (cherry picked from commit e0df0dce71d86796195502b923243bb6bacdcdc2)
---
 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 7c6c4d2bc8a1..bce511463d38 100644
--- a/sys/dev/powermac_nvram/powermac_nvram.c
+++ b/sys/dev/powermac_nvram/powermac_nvram.c
@@ -362,7 +362,7 @@ 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];