6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pauli Virtanen [ Upstream commit ca2c4c26498643f421d35ffe258fafbd3ed461c3 ] Since commit b66774b48dd9 ("Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref") l2cap_chan::conn has held reference and remains non-NULL also after the corresponding hci_conn is deleted. In this state accessing various fields eg. hci_conn::hdev is invalid, which leads to KASAN crash in l2cap_sock_setsockopt() access of conn->hcon->hdev. Check l2cap_chan::conn.hcon corresponds to an alive hci_conn before trying to use it in l2cap_sock.c. Hold l2cap_chan_lock() in getsockopt/setsockopt to ensure it stays alive, and to avoid data races in l2cap_chan fields. Fixes: b66774b48dd9 ("Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref") Reported-by: syzbot+b106284c2a0b7bc80cf9@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=b106284c2a0b7bc80cf9 Signed-off-by: Pauli Virtanen Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/l2cap_sock.c | 57 ++++++++++++++++++++++++++++++-------- 1 file changed, 46 insertions(+), 11 deletions(-) diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index d09a0b0ffd0c1..c0da2b1168a1f 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -437,11 +437,26 @@ static int l2cap_get_mode(struct l2cap_chan *chan) return -EINVAL; } +static struct l2cap_conn *l2cap_chan_conn(struct l2cap_chan *chan) +{ + lockdep_assert_held(&chan->lock); + + /* l2cap_conn_del() sets FLAG_DEL while holding chan->lock before + * conn->hcon is deleted. If not set and conn is non-NULL, conn->hcon + * remains alive during this chan->lock critical section. + */ + if (test_bit(FLAG_DEL, &chan->flags)) + return NULL; + + return chan->conn; +} + static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, char __user *optval, int __user *optlen) { struct sock *sk = sock->sk; struct l2cap_chan *chan = l2cap_pi(sk)->chan; + struct l2cap_conn *conn; struct l2cap_options opts; struct l2cap_conninfo cinfo; int err = 0; @@ -453,6 +468,7 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, if (get_user(len, optlen)) return -EFAULT; + l2cap_chan_lock(chan); lock_sock(sk); switch (optname) { @@ -538,9 +554,15 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, break; } + conn = l2cap_chan_conn(chan); + if (!conn) { + err = -ENOTCONN; + break; + } + memset(&cinfo, 0, sizeof(cinfo)); - cinfo.hci_handle = chan->conn->hcon->handle; - memcpy(cinfo.dev_class, chan->conn->hcon->dev_class, 3); + cinfo.hci_handle = conn->hcon->handle; + memcpy(cinfo.dev_class, conn->hcon->dev_class, 3); len = min(len, sizeof(cinfo)); if (copy_to_user(optval, (char *) &cinfo, len)) @@ -554,6 +576,8 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, } release_sock(sk); + l2cap_chan_unlock(chan); + return err; } @@ -562,6 +586,7 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname, { struct sock *sk = sock->sk; struct l2cap_chan *chan = l2cap_pi(sk)->chan; + struct l2cap_conn *conn; struct bt_security sec; struct bt_power pwr; u32 phys; @@ -578,6 +603,7 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname, if (get_user(len, optlen)) return -EFAULT; + l2cap_chan_lock(chan); lock_sock(sk); switch (optname) { @@ -589,12 +615,14 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname, break; } + conn = l2cap_chan_conn(chan); + memset(&sec, 0, sizeof(sec)); - if (chan->conn) { - sec.level = chan->conn->hcon->sec_level; + if (conn) { + sec.level = conn->hcon->sec_level; if (sk->sk_state == BT_CONNECTED) - sec.key_size = chan->conn->hcon->enc_key_size; + sec.key_size = conn->hcon->enc_key_size; } else { sec.level = chan->sec_level; } @@ -670,12 +698,14 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname, break; case BT_PHY: - if (sk->sk_state != BT_CONNECTED) { + conn = l2cap_chan_conn(chan); + + if (sk->sk_state != BT_CONNECTED || !conn) { err = -ENOTCONN; break; } - phys = hci_conn_get_phy(chan->conn->hcon); + phys = hci_conn_get_phy(conn->hcon); if (put_user(phys, (u32 __user *) optval)) err = -EFAULT; @@ -708,6 +738,7 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname, } release_sock(sk); + l2cap_chan_unlock(chan); return err; } @@ -738,6 +769,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, BT_DBG("sk %p", sk); + l2cap_chan_lock(chan); lock_sock(sk); switch (optname) { @@ -838,6 +870,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, } release_sock(sk); + l2cap_chan_unlock(chan); return err; } @@ -901,6 +934,7 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, if (level != SOL_BLUETOOTH) return -ENOPROTOOPT; + l2cap_chan_lock(chan); lock_sock(sk); switch (optname) { @@ -926,11 +960,10 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, chan->sec_level = sec.level; - if (!chan->conn) + conn = l2cap_chan_conn(chan); + if (!conn) break; - conn = chan->conn; - /* change security for LE channels */ if (chan->scid == L2CAP_CID_ATT) { if (smp_conn_security(conn->hcon, sec.level)) { @@ -985,7 +1018,8 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, } if (opt == BT_FLUSHABLE_OFF) { - conn = chan->conn; + conn = l2cap_chan_conn(chan); + /* proceed further only when we have l2cap_conn and No Flush support in the LM */ if (!conn || !lmp_no_flush_capable(conn->hcon->hdev)) { @@ -1108,6 +1142,7 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, } release_sock(sk); + l2cap_chan_unlock(chan); return err; } -- 2.53.0