2024-01-03 04:06:36

by Yuxuan Hu

[permalink] [raw]
Subject: [PATCH V2] Bluetooth: rfcomm: Fix null-ptr-deref in rfcomm_check_security

During our fuzz testing of the connection and disconnection process at the
RFCOMM layer,we discovered this bug.By comparing the packetsfrom a normal
connection and disconnection process with the testcase that triggered a
KASAN report, we analyzed the cause of this bug as follows:

1. In the packets captured during a normal connection, the host sends a
`Read Encryption Key Size` type of `HCI_CMD` packet(Command Opcode: 0x1408)
to the controller to inquire the length of encryption key.After receiving
this packet, the controller immediately replies with a Command Complete
packet (Event Code: 0x0e) to return the Encryption Key Size.

2. In our fuzz test case, the timing of the controller's response to this
packet was delayed to an unexpected point: after the RFCOMM and L2CAP
layers had disconnected but before the HCI layer had disconnected.

3. After receiving the Encryption Key Size Response at the time described
in point 2, the host still called the rfcomm_check_security function.
However, by this time `struct l2cap_conn *conn = l2cap_pi(sk)->chan->conn;`
had already been released, and when the function executed
`return hci_conn_security(conn->hcon, d->sec_level, auth_type, d->out);`,
specifically when accessing `conn->hcon`, a null-ptr-deref error occurred.

To fix this bug, check if `sk->sk_state` is BT_CLOSED before calling
rfcomm_recv_frame in rfcomm_process_rx.

Signed-off-by: Yuxuan Hu <[email protected]>
V1 -> V2: Check earlier on rfcomm_process_rx

net/bluetooth/rfcomm/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index 053ef8f25fae..1d34d8497033 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -1941,7 +1941,7 @@ static struct rfcomm_session *rfcomm_process_rx(struct rfcomm_session *s)
/* Get data directly from socket receive queue without copying it. */
while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
- if (!skb_linearize(skb)) {
+ if (!skb_linearize(skb) && sk->sk_state != BT_CLOSED) {
s = rfcomm_recv_frame(s, skb);
if (!s)

2024-01-03 04:35:01

by bluez.test.bot

[permalink] [raw]
Subject: RE: [V2] Bluetooth: rfcomm: Fix null-ptr-deref in rfcomm_check_security

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=813996

---Test result---

Test Summary:
CheckPatch PASS 0.59 seconds
GitLint PASS 0.30 seconds
SubjectPrefix PASS 0.11 seconds
BuildKernel PASS 28.36 seconds
CheckAllWarning PASS 30.79 seconds
CheckSparse PASS 36.29 seconds
CheckSmatch PASS 99.59 seconds
BuildKernel32 PASS 27.30 seconds
TestRunnerSetup PASS 435.31 seconds
TestRunner_l2cap-tester PASS 22.95 seconds
TestRunner_iso-tester PASS 47.20 seconds
TestRunner_bnep-tester PASS 6.82 seconds
TestRunner_mgmt-tester FAIL 167.67 seconds
TestRunner_rfcomm-tester PASS 10.89 seconds
TestRunner_sco-tester PASS 14.55 seconds
TestRunner_ioctl-tester PASS 12.12 seconds
TestRunner_mesh-tester PASS 9.14 seconds
TestRunner_smp-tester PASS 9.79 seconds
TestRunner_userchan-tester PASS 7.19 seconds
IncrementalBuild PASS 26.29 seconds

Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Total: 497, Passed: 495 (99.6%), Failed: 1, Not Run: 1

Failed Test Cases
LL Privacy - Start Discovery 2 (Disable RL) Failed 0.295 seconds

Linux Bluetooth