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From:   Pavel Skripkin <paskripkin@gmail.com>
To:     alex.aring@gmail.com, stefan@datenfreihafen.org,
        davem@davemloft.net
Cc:     linux-wpan@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Pavel Skripkin <paskripkin@gmail.com>,
        syzbot+7bf7b22759195c9a21e9@syzkaller.appspotmail.com
Subject: [PATCH] net: fix shift-out-of-bounds in nl802154_new_interface
Date:   Mon,  5 Apr 2021 22:57:44 +0300
Message-Id: <20210405195744.19386-1-paskripkin@gmail.com>
MIME-Version: 1.0
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syzbot reported shift-out-of-bounds in nl802154_new_interface.
The problem was in signed representation of enum nl802154_iftype

enum nl802154_iftype {
	/* for backwards compatibility TODO */
	NL802154_IFTYPE_UNSPEC = -1,
...

Since, enum has negative value in it, objects of this type
will be represented as signed integer.

	type = nla_get_u32(info->attrs[NL802154_ATTR_IFTYPE]);

u32 will be casted to signed, which can cause negative value type.

Reported-by: syzbot+7bf7b22759195c9a21e9@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 net/ieee802154/nl802154.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ieee802154/nl802154.c b/net/ieee802154/nl802154.c
index 7c5a1aa5adb4..6cce045e3d40 100644
--- a/net/ieee802154/nl802154.c
+++ b/net/ieee802154/nl802154.c
@@ -910,7 +910,7 @@ static int nl802154_new_interface(struct sk_buff *skb, struct genl_info *info)
 
 	if (info->attrs[NL802154_ATTR_IFTYPE]) {
 		type = nla_get_u32(info->attrs[NL802154_ATTR_IFTYPE]);
-		if (type > NL802154_IFTYPE_MAX ||
+		if (type > NL802154_IFTYPE_MAX || type < 0 ||
 		    !(rdev->wpan_phy.supported.iftypes & BIT(type)))
 			return -EINVAL;
 	}
-- 
2.30.2