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([129.170.197.108]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8d028095f1csm819343585a.47.2026.03.30.15.10.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 15:10:16 -0700 (PDT) From: Nathan Rebello To: linux-bluetooth@vger.kernel.org Cc: luiz.dentz@gmail.com, marcel@holtmann.org, stable@vger.kernel.org, kyungtae.kim@dartmouth.edu, Nathan Rebello Subject: [PATCH v3] Bluetooth: ISO: fix NULL deref in iso_recv() ISO_END handling Date: Mon, 30 Mar 2026 18:10:15 -0400 Message-ID: <20260330221015.322337-1-nathan.c.rebello@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260328035813.296410-1-nathan.c.rebello@gmail.com> References: <20260328035813.296410-1-nathan.c.rebello@gmail.com> Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The ISO_CONT case in iso_recv() properly checks for unexpected continuation frames and oversized fragments before accessing conn->rx_skb. The ISO_END case lacks both checks. When an ISO_END packet arrives without a preceding ISO_START: - conn->rx_skb is NULL (never allocated) - skb_put(conn->rx_skb, ...) dereferences NULL -> kernel crash When an ISO_END fragment length does not exactly match the remaining expected length: - the reassembly is malformed and must be rejected KASAN confirmed the NULL-deref on kernel 7.0.0-rc5 via VHCI: general protection fault, probably for non-canonical address 0xdffffc0000000018 KASAN: null-ptr-deref in range [0x00000000000000c0-0x00000000000000c7] CPU: 0 UID: 0 PID: 72 Comm: kworker/u9:0 Not tainted 7.0.0-rc5 Workqueue: hci0 hci_rx_work RIP: 0010:skb_put+0x27/0x1a0 Call Trace: iso_recv+0x5e0/0xee0 hci_rx_work+0x226/0x730 process_one_work+0x633/0x1060 worker_thread+0x45b/0xd10 kthread+0x2c6/0x3b0 ret_from_fork+0x38d/0x5c0 Kernel panic - not syncing: Fatal exception Fix by adding validation to the ISO_END case: reject end frames when no rx_skb reassembly buffer exists, and reject end fragments whose length does not exactly complete the expected reassembly. Fixes: ccf74f2390d6 ("Bluetooth: Add ISO Socket") Cc: stable@vger.kernel.org Signed-off-by: Nathan Rebello --- Changes in v3: - Check !conn->rx_skb instead of !conn->rx_len to correctly handle the case where an ISO_CONT fragment completes rx_len but a valid zero-length ISO_END still follows. Changes in v2: - Tighten end fragment check from (skb->len > conn->rx_len) to (skb->len != conn->rx_len): the end fragment must exactly complete the reassembly. net/bluetooth/iso.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c index be145e273..7c57b1d22 100644 --- a/net/bluetooth/iso.c +++ b/net/bluetooth/iso.c @@ -2587,6 +2587,20 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags) break; case ISO_END: + if (!conn->rx_skb) { + BT_ERR("Unexpected end frame (len %d)", skb->len); + goto drop; + } + + if (skb->len != conn->rx_len) { + BT_ERR("End fragment length mismatch (len %d, expected %d)", + skb->len, conn->rx_len); + kfree_skb(conn->rx_skb); + conn->rx_skb = NULL; + conn->rx_len = 0; + goto drop; + } + skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len), skb->len); conn->rx_len -= skb->len; -- 2.43.0