[PATCH] Bluetooth: L2CAP: Add missing checks for invalid DCID

When receiving a connect response we should make sure that the DCID is
within the valid range and that we don't already have another channel
allocated for the same DCID.
Missing checks may violate the specification (BLUETOOTH CORE SPECIFICATION
Version 5.4 | Vol 3, Part A, Page 1046).

Fixes: 40624183c202 ("L2CAP: Add missing checks for invalid LE DCID")
Signed-off-by: Sungwoo Kim <redacted>
---
 net/bluetooth/l2cap_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 376b523c7..104eb0320 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c

@@ -4306,6 +4306,10 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 	result = __le16_to_cpu(rsp->result);
 	status = __le16_to_cpu(rsp->status);
 
+	if (result == L2CAP_CR_SUCCESS && (dcid < L2CAP_CID_DYN_START ||
+					   dcid > L2CAP_CID_DYN_END))
+		return -EPROTO;
+
 	BT_DBG("dcid 0x%4.4x scid 0x%4.4x result 0x%2.2x status 0x%2.2x",
 	       dcid, scid, result, status);
 

@@ -4337,6 +4341,11 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
 
 	switch (result) {
 	case L2CAP_CR_SUCCESS:
+		if (__l2cap_get_chan_by_dcid(conn, dcid)) {
+			err = -EBADSLT;
+			break;
+		}
+
 		l2cap_state_change(chan, BT_CONFIG);
 		chan->ident = 0;
 		chan->dcid = dcid;

-- 
2.34.1

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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=753751

---Test result---

Test Summary:
CheckPatch                    PASS      0.74 seconds
GitLint                       PASS      0.36 seconds
SubjectPrefix                 PASS      0.13 seconds
BuildKernel                   PASS      33.11 seconds
CheckAllWarning               PASS      36.05 seconds
CheckSparse                   PASS      41.35 seconds
CheckSmatch                   PASS      111.10 seconds
BuildKernel32                 PASS      32.14 seconds
TestRunnerSetup               PASS      457.37 seconds
TestRunner_l2cap-tester       PASS      17.54 seconds
TestRunner_iso-tester         PASS      24.19 seconds
TestRunner_bnep-tester        PASS      5.88 seconds
TestRunner_mgmt-tester        PASS      118.33 seconds
TestRunner_rfcomm-tester      PASS      9.11 seconds
TestRunner_sco-tester         PASS      8.40 seconds
TestRunner_ioctl-tester       PASS      9.93 seconds
TestRunner_mesh-tester        PASS      7.35 seconds
TestRunner_smp-tester         PASS      8.71 seconds
TestRunner_userchan-tester    PASS      6.01 seconds
IncrementalBuild              PASS      30.61 seconds



---
Regards,
Linux Bluetooth

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz [off-list ref]:

On Sat,  3 Jun 2023 08:28:09 -0400 you wrote:

When receiving a connect response we should make sure that the DCID is
within the valid range and that we don't already have another channel
allocated for the same DCID.
Missing checks may violate the specification (BLUETOOTH CORE SPECIFICATION
Version 5.4 | Vol 3, Part A, Page 1046).

Fixes: 40624183c202 ("L2CAP: Add missing checks for invalid LE DCID")
Signed-off-by: Sungwoo Kim <redacted>

[...]

Here is the summary with links:
  - Bluetooth: L2CAP: Add missing checks for invalid DCID
    https://git.kernel.org/bluetooth/bluetooth-next/c/f9367ce74db3

You are awesome, thank you!
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