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author | Maxim Mikityanskiy <maxtram95@gmail.com> | 2022-10-04 23:27:18 +0200 |
---|---|---|
committer | Luiz Augusto von Dentz <luiz.von.dentz@intel.com> | 2022-11-02 22:12:34 +0100 |
commit | 3aff8aaca4e36dc8b17eaa011684881a80238966 (patch) | |
tree | a7f5cac74679edf1ae891378fc935c95be9cef8d /net/bluetooth | |
parent | Merge branch 'misdn-fixes' (diff) | |
download | linux-3aff8aaca4e36dc8b17eaa011684881a80238966.tar.xz linux-3aff8aaca4e36dc8b17eaa011684881a80238966.zip |
Bluetooth: L2CAP: Fix use-after-free caused by l2cap_reassemble_sdu
Fix the race condition between the following two flows that run in
parallel:
1. l2cap_reassemble_sdu -> chan->ops->recv (l2cap_sock_recv_cb) ->
__sock_queue_rcv_skb.
2. bt_sock_recvmsg -> skb_recv_datagram, skb_free_datagram.
An SKB can be queued by the first flow and immediately dequeued and
freed by the second flow, therefore the callers of l2cap_reassemble_sdu
can't use the SKB after that function returns. However, some places
continue accessing struct l2cap_ctrl that resides in the SKB's CB for a
short time after l2cap_reassemble_sdu returns, leading to a
use-after-free condition (the stack trace is below, line numbers for
kernel 5.19.8).
Fix it by keeping a local copy of struct l2cap_ctrl.
BUG: KASAN: use-after-free in l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth
Read of size 1 at addr ffff88812025f2f0 by task kworker/u17:3/43169
Workqueue: hci0 hci_rx_work [bluetooth]
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4))
print_report.cold (mm/kasan/report.c:314 mm/kasan/report.c:429)
? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth
kasan_report (mm/kasan/report.c:162 mm/kasan/report.c:493)
? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth
l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth
l2cap_rx (net/bluetooth/l2cap_core.c:7236 net/bluetooth/l2cap_core.c:7271) bluetooth
ret_from_fork (arch/x86/entry/entry_64.S:306)
</TASK>
Allocated by task 43169:
kasan_save_stack (mm/kasan/common.c:39)
__kasan_slab_alloc (mm/kasan/common.c:45 mm/kasan/common.c:436 mm/kasan/common.c:469)
kmem_cache_alloc_node (mm/slab.h:750 mm/slub.c:3243 mm/slub.c:3293)
__alloc_skb (net/core/skbuff.c:414)
l2cap_recv_frag (./include/net/bluetooth/bluetooth.h:425 net/bluetooth/l2cap_core.c:8329) bluetooth
l2cap_recv_acldata (net/bluetooth/l2cap_core.c:8442) bluetooth
hci_rx_work (net/bluetooth/hci_core.c:3642 net/bluetooth/hci_core.c:3832) bluetooth
process_one_work (kernel/workqueue.c:2289)
worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
kthread (kernel/kthread.c:376)
ret_from_fork (arch/x86/entry/entry_64.S:306)
Freed by task 27920:
kasan_save_stack (mm/kasan/common.c:39)
kasan_set_track (mm/kasan/common.c:45)
kasan_set_free_info (mm/kasan/generic.c:372)
____kasan_slab_free (mm/kasan/common.c:368 mm/kasan/common.c:328)
slab_free_freelist_hook (mm/slub.c:1780)
kmem_cache_free (mm/slub.c:3536 mm/slub.c:3553)
skb_free_datagram (./include/net/sock.h:1578 ./include/net/sock.h:1639 net/core/datagram.c:323)
bt_sock_recvmsg (net/bluetooth/af_bluetooth.c:295) bluetooth
l2cap_sock_recvmsg (net/bluetooth/l2cap_sock.c:1212) bluetooth
sock_read_iter (net/socket.c:1087)
new_sync_read (./include/linux/fs.h:2052 fs/read_write.c:401)
vfs_read (fs/read_write.c:482)
ksys_read (fs/read_write.c:620)
do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
Link: https://lore.kernel.org/linux-bluetooth/CAKErNvoqga1WcmoR3-0875esY6TVWFQDandbVZncSiuGPBQXLA@mail.gmail.com/T/#u
Fixes: d2a7ac5d5d3a ("Bluetooth: Add the ERTM receive state machine")
Fixes: 4b51dae96731 ("Bluetooth: Add streaming mode receive and incoming packet classifier")
Signed-off-by: Maxim Mikityanskiy <maxtram95@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Diffstat (limited to 'net/bluetooth')
-rw-r--r-- | net/bluetooth/l2cap_core.c | 48 |
1 files changed, 41 insertions, 7 deletions
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 1f34b82ca0ec..2283871d3f01 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -6885,6 +6885,7 @@ static int l2cap_rx_state_recv(struct l2cap_chan *chan, struct l2cap_ctrl *control, struct sk_buff *skb, u8 event) { + struct l2cap_ctrl local_control; int err = 0; bool skb_in_use = false; @@ -6909,15 +6910,32 @@ static int l2cap_rx_state_recv(struct l2cap_chan *chan, chan->buffer_seq = chan->expected_tx_seq; skb_in_use = true; + /* l2cap_reassemble_sdu may free skb, hence invalidate + * control, so make a copy in advance to use it after + * l2cap_reassemble_sdu returns and to avoid the race + * condition, for example: + * + * The current thread calls: + * l2cap_reassemble_sdu + * chan->ops->recv == l2cap_sock_recv_cb + * __sock_queue_rcv_skb + * Another thread calls: + * bt_sock_recvmsg + * skb_recv_datagram + * skb_free_datagram + * Then the current thread tries to access control, but + * it was freed by skb_free_datagram. + */ + local_control = *control; err = l2cap_reassemble_sdu(chan, skb, control); if (err) break; - if (control->final) { + if (local_control.final) { if (!test_and_clear_bit(CONN_REJ_ACT, &chan->conn_state)) { - control->final = 0; - l2cap_retransmit_all(chan, control); + local_control.final = 0; + l2cap_retransmit_all(chan, &local_control); l2cap_ertm_send(chan); } } @@ -7297,11 +7315,27 @@ static int l2cap_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, static int l2cap_stream_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, struct sk_buff *skb) { + /* l2cap_reassemble_sdu may free skb, hence invalidate control, so store + * the txseq field in advance to use it after l2cap_reassemble_sdu + * returns and to avoid the race condition, for example: + * + * The current thread calls: + * l2cap_reassemble_sdu + * chan->ops->recv == l2cap_sock_recv_cb + * __sock_queue_rcv_skb + * Another thread calls: + * bt_sock_recvmsg + * skb_recv_datagram + * skb_free_datagram + * Then the current thread tries to access control, but it was freed by + * skb_free_datagram. + */ + u16 txseq = control->txseq; + BT_DBG("chan %p, control %p, skb %p, state %d", chan, control, skb, chan->rx_state); - if (l2cap_classify_txseq(chan, control->txseq) == - L2CAP_TXSEQ_EXPECTED) { + if (l2cap_classify_txseq(chan, txseq) == L2CAP_TXSEQ_EXPECTED) { l2cap_pass_to_tx(chan, control); BT_DBG("buffer_seq %u->%u", chan->buffer_seq, @@ -7324,8 +7358,8 @@ static int l2cap_stream_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, } } - chan->last_acked_seq = control->txseq; - chan->expected_tx_seq = __next_seq(chan, control->txseq); + chan->last_acked_seq = txseq; + chan->expected_tx_seq = __next_seq(chan, txseq); return 0; } |