linux-kernel - [PATCH v2] Bluetooth: add timeout sanity check to hci

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Message-Id: <20210819151521.17380-1-paskripkin@gmail.com>
Date:   Thu, 19 Aug 2021 18:15:21 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com,
        davem@...emloft.net
Cc:     linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+be2baed593ea56c6a84c@...kaller.appspotmail.com
Subject: [PATCH v2] Bluetooth: add timeout sanity check to hci_inquiry

Syzbot hit "task hung" bug in hci_req_sync(). The problem was in
unreasonable huge inquiry timeout passed from userspace.
Fix it by adding sanity check for timeout value to hci_inquiry().

Since hci_inquiry() is the only user of hci_req_sync() with user
controlled timeout value, it makes sense to check timeout value in
hci_inquiry() and don't touch hci_req_sync().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-and-tested-by: syzbot+be2baed593ea56c6a84c@...kaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---

Changes in v2:
	Removed define + added comment suggested by Marcel

---
 net/bluetooth/hci_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index e1a545c8a69f..170f513efa86 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1343,6 +1343,12 @@ int hci_inquiry(void __user *arg)
 		goto done;
 	}
 
+	/* Restrict maximum inquiry length to 60 seconds */
+	if (ir.length > 60) {
+		err = -EINVAL;
+		goto done;
+	}
+
 	hci_dev_lock(hdev);
 	if (inquiry_cache_age(hdev) > INQUIRY_CACHE_AGE_MAX ||
 	    inquiry_cache_empty(hdev) || ir.flags & IREQ_CACHE_FLUSH) {
-- 
2.32.0