[PATCH v2] Bluetooth: mgmt: fix race in read_unconf_index_list()

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

read_unconf_index_list() counts unconfigured controllers before allocating
its response, then checks the device flags again while filling it.

hci_dev_list_lock stabilizes list membership, but it does not serialize the
per-device flags. During asynchronous controller setup, the worker can set
HCI_UNCONFIGURED and clear HCI_SETUP between the two passes. A controller
omitted from the allocation count can then become eligible for the fill
pass, causing an out-of-bounds write to rp->index[].

Allocate space for every device on hci_dev_list. Since list membership
cannot change while hci_dev_list_lock is held, the response remains large
enough regardless of flag transitions. The reported count and response
length still include only eligible unconfigured controllers.

Fixes: 73d1df2a7a10 ("Bluetooth: Add support for Read Unconfigured Index List command")
Cc: stable@vger.kernel.org
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
---
 net/bluetooth/mgmt.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 167d75e34..1f6691278 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -496,13 +496,9 @@ static int read_unconf_index_list(struct sock *sk, struct hci_dev *hdev,
 
 	read_lock(&hci_dev_list_lock);
 
-	count = 0;
-	list_for_each_entry(d, &hci_dev_list, list) {
-		if (hci_dev_test_flag(d, HCI_UNCONFIGURED))
-			count++;
-	}
+	count = list_count_nodes(&hci_dev_list);
 
-	rp_len = sizeof(*rp) + (2 * count);
+	rp_len = sizeof(*rp) + (sizeof(__le16) * count);
 	rp = kmalloc(rp_len, GFP_ATOMIC);
 	if (!rp) {
 		read_unlock(&hci_dev_list_lock);
-- 
2.43.0