linux-kernel - Re: [syzbot] [input?] [usb?] UBSAN: shift-out-of-bounds in s32ton

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Message-Id: <20241114014002.7435-2-xiaopei01@kylinos.cn>
Date: Thu, 14 Nov 2024 09:40:02 +0800
From: Pei Xiao <xiaopei01@...inos.cn>
To: syzbot+3fa2af55f15bd21cada9@...kaller.appspotmail.com,
	linux-kernel@...r.kernel.org
Cc: xiaopei01@...inos.cn
Subject: Re: [syzbot] [input?] [usb?] UBSAN: shift-out-of-bounds in s32ton

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 81d6c734c8bc..ead1d338fa58 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -66,8 +66,11 @@ static s32 snto32(__u32 value, unsigned int n)
 
 static u32 s32ton(__s32 value, unsigned int n)
 {
-	s32 a = value >> (n - 1);
+	s32 a;
 
+	if (n >= 32)
+		return value;
+	a = value >> (n - 1);
 	if (a && a != -1)
 		return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1;
 	return value & ((1 << n) - 1);