Hi Pauli,
On Tue, Jul 16, 2024 at 3:00 PM Pauli Virtanen pav@iki.fi wrote:
Hi,
ti, 2024-07-16 kello 10:24 -0400, Sasha Levin kirjoitti:
From: Edward Adam Davis eadavis@qq.com
[ Upstream commit 89e856e124f9ae548572c56b1b70c2255705f8fe ]
This one needed an additional fixup that I don't see AUTOSEL picked up, otherwise it results to a worse regression:
https://lore.kernel.org/linux-bluetooth/20240624134637.3790278-1-luiz.dentz@...
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
Looks like f1a8f402f13f94263cf349216c257b2985100927 also contains other changes not related to this patch, seems like https://lore.kernel.org/linux-bluetooth/20240624144911.3817479-1-luiz.dentz@... was squashed.
Yep, it seems I messed them up while doing the pull-request and 2 commits were merged together, not sure if we can rebase them now that are in Linus tree, anyway for stable it would be better to unmerge them if possible.
The problem occurs between the system call to close the sock and hci_rx_work, where the former releases the sock and the latter accesses it without lock protection.
CPU0 CPU1 ---- ---- sock_close hci_rx_work l2cap_sock_release hci_acldata_packet l2cap_sock_kill l2cap_recv_frame sk_free l2cap_conless_channel l2cap_sock_recv_cbIf hci_rx_work processes the data that needs to be received before the sock is closed, then everything is normal; Otherwise, the work thread may access the released sock when receiving data.
Add a chan mutex in the rx callback of the sock to achieve synchronization between the sock release and recv cb.
Sock is dead, so set chan data to NULL, avoid others use invalid sock pointer.
Reported-and-tested-by: syzbot+b7f6f8c9303466e16c8a@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis eadavis@qq.com Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org
net/bluetooth/l2cap_sock.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 8645461d45e81..64827e553d638 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1239,6 +1239,10 @@ static void l2cap_sock_kill(struct sock *sk)
BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
/* Sock is dead, so set chan data to NULL, avoid other task use invalid* sock pointer.*/l2cap_pi(sk)->chan->data = NULL; /* Kill poor orphan */ l2cap_chan_put(l2cap_pi(sk)->chan);@@ -1481,12 +1485,25 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(struct l2cap_chan *chan)
static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb) {
struct sock *sk = chan->data;struct l2cap_pinfo *pi = l2cap_pi(sk);
struct sock *sk;struct l2cap_pinfo *pi; int err;
lock_sock(sk);
/* To avoid race with sock_release, a chan lock needs to be added here* to synchronize the sock.*/l2cap_chan_hold(chan);l2cap_chan_lock(chan);sk = chan->data;if (!sk) {l2cap_chan_unlock(chan);l2cap_chan_put(chan);return -ENXIO;}pi = l2cap_pi(sk);lock_sock(sk); if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) { err = -ENOMEM; goto done;@@ -1535,6 +1552,8 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
done: release_sock(sk);
l2cap_chan_unlock(chan);l2cap_chan_put(chan); return err;}
-- Pauli Virtanen