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Fri, 19 Dec 2025 16:27:46 -0800 (PST) Received: from seungjin-HP-ENVY-Desktop-TE02-0xxx.dartmouth.edu ([129.170.197.82]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c096891558sm294631985a.15.2025.12.19.16.27.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Dec 2025 16:27:46 -0800 (PST) From: pip-izony To: Dmitry Torokhov Cc: Seungjin Bae , Kyungtae Kim , Sanghoon Choi , Dan Carpenter , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] Input: ims-pcu - fix heap-buffer-overflow in ims_pcu_process_data() Date: Fri, 19 Dec 2025 19:24:50 -0500 Message-ID: <20251220002447.392843-4-eeodqql09@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Seungjin Bae The `ims_pcu_process_data()` processes incoming URB data byte by byte. However, it fails to check if the `read_pos` index exceeds IMS_PCU_BUF_SIZE. If a malicious USB device sends a packet larger than IMS_PCU_BUF_SIZE, `read_pos` will increment indefinitely. Moreover, since `read_pos` is located immediately after `read_buf`, the attacker can overwrite `read_pos` itself to arbitrarily control the index. This manipulated `read_pos` is subsequently used in `ims_pcu_handle_response()` to copy data into `cmd_buf`, leading to a heap buffer overflow. Specifically, an attacker can overwrite the `cmd_done.wait.head` located at offset 136 relative to `cmd_buf` in the `ims_pcu_handle_response()`. Consequently, when the driver calls `complete(&pcu->cmd_done)`, it triggers a control flow hijack by using the manipulated pointer. Fix this by adding a bounds check for `read_pos` before writing to `read_buf`. If the packet is too long, discard it, log a warining, and reset the parser state. Fixes: 628329d524743 ("Input: add IMS Passenger Control Unit driver") Signed-off-by: Seungjin Bae --- v1 -> v2: Add warning and reset the state of the parser for bad packet drivers/input/misc/ims-pcu.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c index 4581f1c53644..c98ef71c841e 100644 --- a/drivers/input/misc/ims-pcu.c +++ b/drivers/input/misc/ims-pcu.c @@ -450,6 +450,16 @@ static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb) continue; if (pcu->have_dle) { + if (pcu->read_pos >= IMS_PCU_BUF_SIZE) { + dev_warn(pcu->dev, + "Packet too long (%d bytes), discarding\n", + pcu->read_pos); + pcu->have_stx = false; + pcu->have_dle = false; + pcu->read_pos = 0; + continue; + } + pcu->have_dle = false; pcu->read_buf[pcu->read_pos++] = data; pcu->check_sum += data; @@ -491,6 +501,16 @@ static void ims_pcu_process_data(struct ims_pcu *pcu, struct urb *urb) break; default: + if (pcu->read_pos >= IMS_PCU_BUF_SIZE) { + dev_warn(pcu->dev, + "Packet too long (%d bytes), discarding\n", + pcu->read_pos); + pcu->have_stx = false; + pcu->have_dle = false; + pcu->read_pos = 0; + continue; + } + pcu->read_buf[pcu->read_pos++] = data; pcu->check_sum += data; break; -- 2.43.0