On Wed, 22 Jun 2022, Lee Jones wrote:
> This change prevents a use-after-free caused by one of the worker
> threads starting up (see below) *after* the final channel reference
> has been put() during sock_close() but *before* the references to the
> channel have been destroyed.
>
> refcount_t: increment on 0; use-after-free.
> BUG: KASAN: use-after-free in refcount_dec_and_test+0x20/0xd0
> Read of size 4 at addr ffffffc114f5bf18 by task kworker/u17:14/705
>
> CPU: 4 PID: 705 Comm: kworker/u17:14 Tainted: G S W 4.14.234-00003-g1fb6d0bd49a4-dirty #28
> Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM sm8150 Flame DVT (DT)
> Workqueue: hci0 hci_rx_work
> Call trace:
> dump_backtrace+0x0/0x378
> show_stack+0x20/0x2c
> dump_stack+0x124/0x148
> print_address_description+0x80/0x2e8
> __kasan_report+0x168/0x188
> kasan_report+0x10/0x18
> __asan_load4+0x84/0x8c
> refcount_dec_and_test+0x20/0xd0
> l2cap_chan_put+0x48/0x12c
> l2cap_recv_frame+0x4770/0x6550
> l2cap_recv_acldata+0x44c/0x7a4
> hci_acldata_packet+0x100/0x188
> hci_rx_work+0x178/0x23c
> process_one_work+0x35c/0x95c
> worker_thread+0x4cc/0x960
> kthread+0x1a8/0x1c4
> ret_from_fork+0x10/0x18
>
> Cc: stable@xxxxxxxxxx
> Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
> Cc: Johan Hedberg <johan.hedberg@xxxxxxxxx>
> Cc: Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: linux-bluetooth@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
> net/bluetooth/l2cap_core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
This patch now passes all of the CI tests.
Except the check-patch/lint tests which return false positives.
Please consider for inclusion to remedy this serious bug.
TIA.
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index ae78490ecd3d4..82279c5919fd8 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -483,9 +483,7 @@ static void l2cap_chan_destroy(struct kref *kref)
>
> BT_DBG("chan %p", chan);
>
> - write_lock(&chan_list_lock);
> list_del(&chan->global_l);
> - write_unlock(&chan_list_lock);
>
> kfree(chan);
> }
> @@ -501,7 +499,9 @@ void l2cap_chan_put(struct l2cap_chan *c)
> {
> BT_DBG("chan %p orig refcnt %u", c, kref_read(&c->kref));
>
> + write_lock(&chan_list_lock);
> kref_put(&c->kref, l2cap_chan_destroy);
> + write_unlock(&chan_list_lock);
> }
> EXPORT_SYMBOL_GPL(l2cap_chan_put);
>
--
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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