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Sat, 10 Jan 2026 11:22:42 -0800 (PST) Received: from seungjin-HP-ENVY-Desktop-TE02-0xxx.dartmouth.edu ([129.170.197.124]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4ffa8e6257esm92419021cf.31.2026.01.10.11.22.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Jan 2026 11:22:41 -0800 (PST) From: pip-izony To: Greg Kroah-Hartman , Ingo Molnar , Thomas Gleixner Cc: Seungjin Bae , Kyungtae Kim , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] usb: r8a66597-hcd: fix potential divide-by-zero in prepare_packet_read() Date: Sat, 10 Jan 2026 14:22:33 -0500 Message-ID: <20260110192233.31955-1-eeodqql09@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Seungjin Bae The `prepare_packet_read()` function calculates the number of packets required for a transfer by dividing the transfer buffer length by the maximum packet size (`td->maxpacket`). The `td->maxpacket` is initialized in `r8a66597_make_td()` function based on the endpoint descriptor. However, it does not validate whether `td->maxpacket` is zero before using it in the `DIV_ROUND_UP` macro. If a malicious USB device sends a descriptor with `wMaxPacketSize` set to 0, it triggers a divide-by-zero exception (kernel panic). Fix this by ensuring `td->maxpacket` is greater than 0 before performing the division. Fixes: 5d3043586db4 ("USB: r8a66597-hcd: host controller driver for R8A66597") Signed-off-by: Seungjin Bae --- drivers/usb/host/r8a66597-hcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/host/r8a66597-hcd.c b/drivers/usb/host/r8a66597-hcd.c index d21a03cf5c17..445551b4b05f 100644 --- a/drivers/usb/host/r8a66597-hcd.c +++ b/drivers/usb/host/r8a66597-hcd.c @@ -1097,7 +1097,7 @@ static void prepare_packet_read(struct r8a66597 *r8a66597, pipe_start(r8a66597, td->pipe); pipe_irq_enable(r8a66597, urb, td->pipenum); } else { - if (urb->actual_length == 0) { + if (urb->actual_length == 0 && td->maxpacket > 0) { pipe_irq_disable(r8a66597, td->pipenum); pipe_setting(r8a66597, td); pipe_stop(r8a66597, td->pipe); -- 2.43.0