From: Tavian Barnes <tavianator@tavianator.com>
Date: Fri, 21 Jun 2024 20:38:44 +0000 (-0400)
Subject: bcachefs: mean_and_variance: Avoid too-large shift amounts
X-Git-Tag: v6.11-rc1~81^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=73f88592dd1bef38542024ef8223599afc2c41bb;p=thirdparty%2Fkernel%2Flinux.git

bcachefs: mean_and_variance: Avoid too-large shift amounts

Shifting a value by the width of its type or more is undefined.

Signed-off-by: Tavian Barnes <tavianator@tavianator.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---

diff --git a/fs/bcachefs/mean_and_variance.h b/fs/bcachefs/mean_and_variance.h
index 4fcf062dd22c7..47e4a3c3d26e7 100644
--- a/fs/bcachefs/mean_and_variance.h
+++ b/fs/bcachefs/mean_and_variance.h
@@ -111,11 +111,11 @@ static inline u128_u u128_shl(u128_u i, s8 shift)
 {
 	u128_u r;
 
-	r.lo = i.lo << shift;
+	r.lo = i.lo << (shift & 63);
 	if (shift < 64)
-		r.hi = (i.hi << shift) | (i.lo >> (64 - shift));
+		r.hi = (i.hi << (shift & 63)) | (i.lo >> (-shift & 63));
 	else {
-		r.hi = i.lo << (shift - 64);
+		r.hi = i.lo << (-shift & 63);
 		r.lo = 0;
 	}
 	return r;