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Bluetooth: Fix UAF in hci_conn_hash_flush again

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Commit 06149746e7 ("Bluetooth: hci_conn: Add support for linking
multiple hcon") reintroduced a previously fixed bug [1] ("KASAN:
slab-use-after-free Read in hci_conn_hash_flush"). This bug was
originally fixed by commit 5dc7d23e16 ("Bluetooth: hci_conn: Fix
possible UAF").

The hci_conn_unlink function was added to avoid invalidating the link
traversal caused by successive hci_conn_del operations releasing extra
connections. However, currently hci_conn_unlink itself also releases
extra connections, resulted in the reintroduced bug.

This patch follows a more robust solution for cleaning up all
connections, by repeatedly removing the first connection until there are
none left. This approach does not rely on the inner workings of
hci_conn_del and ensures proper cleanup of all connections.

Meanwhile, we need to make sure that hci_conn_del never fails. Indeed it
doesn't, as it now always returns zero. To make this a bit clearer, this
patch also changes its return type to void.

Reported-by: syzbot+8bb72f86fc823817bc5d@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-bluetooth/000000000000aa920505f60d25ad@google.com/
Fixes: 06149746e7 ("Bluetooth: hci_conn: Add support for linking multiple hcon")
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
Co-developed-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Ruihan Li 2023-05-03 21:39:36 +08:00 committed by Luiz Augusto von Dentz
parent 2910431ab0
commit a2ac591cb4
2 changed files with 23 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/bluetooth/hci_core.h
View File

@ -1327,7 +1327,7 @@ int hci_le_create_cis(struct hci_conn *conn);
struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
u8 role);
int hci_conn_del(struct hci_conn *conn);
void hci_conn_del(struct hci_conn *conn);
void hci_conn_hash_flush(struct hci_dev *hdev);
void hci_conn_check_pending(struct hci_dev *hdev);

33
net/bluetooth/hci_conn.c
View File

@ -1088,6 +1088,14 @@ static void hci_conn_unlink(struct hci_conn *conn)
hci_conn_unlink(child);
/* If hdev is down it means
* hci_dev_close_sync/hci_conn_hash_flush is in progress
* and links don't need to be cleanup as all connections
* would be cleanup.
*/
if (!test_bit(HCI_UP, &hdev->flags))
continue;
/* Due to race, SCO connection might be not established
* yet at this point. Delete it now, otherwise it is
* possible for it to be stuck and can't be deleted.
@ -1112,7 +1120,7 @@ static void hci_conn_unlink(struct hci_conn *conn)
conn->link = NULL;
}
int hci_conn_del(struct hci_conn *conn)
void hci_conn_del(struct hci_conn *conn)
{
struct hci_dev *hdev = conn->hdev;
@ -1163,8 +1171,6 @@ int hci_conn_del(struct hci_conn *conn)
* rest of hci_conn_del.
*/
hci_conn_cleanup(conn);
return 0;
}
struct hci_dev *hci_get_route(bdaddr_t *dst, bdaddr_t *src, uint8_t src_type)
@ -2465,22 +2471,27 @@ timer:
/* Drop all connection on the device */
void hci_conn_hash_flush(struct hci_dev *hdev)
{
struct hci_conn_hash *h = &hdev->conn_hash;
struct hci_conn *c, *n;
struct list_head *head = &hdev->conn_hash.list;
struct hci_conn *conn;
BT_DBG("hdev %s", hdev->name);
list_for_each_entry_safe(c, n, &h->list, list) {
c->state = BT_CLOSED;
hci_disconn_cfm(c, HCI_ERROR_LOCAL_HOST_TERM);
/* We should not traverse the list here, because hci_conn_del
* can remove extra links, which may cause the list traversal
* to hit items that have already been released.
*/
while ((conn = list_first_entry_or_null(head,
struct hci_conn,
list)) != NULL) {
conn->state = BT_CLOSED;
hci_disconn_cfm(conn, HCI_ERROR_LOCAL_HOST_TERM);
/* Unlink before deleting otherwise it is possible that
* hci_conn_del removes the link which may cause the list to
* contain items already freed.
*/
hci_conn_unlink(c);
hci_conn_del(c);
hci_conn_unlink(conn);
hci_conn_del(conn);
}
}