netdev - [PATCH] drivers: net: bsd_comp: fix integer overflow in bsd

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Message-ID: <20240812084312.14127-1-r.smirnov@omp.ru>
Date: Mon, 12 Aug 2024 11:43:11 +0300
From: Roman Smirnov <r.smirnov@....ru>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Breno Leitao <leitao@...ian.org>
CC: Roman Smirnov <r.smirnov@....ru>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Karina Yankevich <k.yankevich@....ru>, Sergey
 Shtylyov <s.shtylyov@....ru>, <lvc-project@...uxtesting.org>
Subject: [PATCH] drivers: net: bsd_comp: fix integer overflow in bsd_decompress()

The result of a bit shift has type int. If ibuf is greater than or
equal to 128, a sign switch will occur. After that, the higher 32
bits in accm will be set to 1.

Cast the result of the expression to unsigned long.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smirnov@....ru>
---
 drivers/net/ppp/bsd_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ppp/bsd_comp.c b/drivers/net/ppp/bsd_comp.c
index 55954594e157..078fe8c9bee8 100644
--- a/drivers/net/ppp/bsd_comp.c
+++ b/drivers/net/ppp/bsd_comp.c
@@ -918,7 +918,7 @@ static int bsd_decompress (void *state, unsigned char *ibuf, int isize,
 	 */
 
 	bitno -= 8;
-	accm  |= *ibuf++ << bitno;
+	accm  |= (unsigned long)(*ibuf++) << bitno;
 	if (tgtbitno < bitno)
 	  {
 	    continue;
-- 
2.43.0