6.17-stable review patch. If anyone has any objections, please let me know.
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From: Dominique Martinet asmadeus@codewreck.org
commit c04db81cd0288dfc68b7a0f7d09bd49b40bba451 upstream.
A buffer overflow vulnerability exists in the USB 9pfs transport layer where inconsistent size validation between packet header parsing and actual data copying allows a malicious USB host to overflow heap buffers.
The issue occurs because: - usb9pfs_rx_header() validates only the declared size in packet header - usb9pfs_rx_complete() uses req->actual (actual received bytes) for memcpy
This allows an attacker to craft packets with small declared size (bypassing validation) but large actual payload (triggering overflow in memcpy).
Add validation in usb9pfs_rx_complete() to ensure req->actual does not exceed the buffer capacity before copying data.
Reported-by: Yuhao Jiang danisjiang@gmail.com Closes: https://lkml.kernel.org/r/20250616132539.63434-1-danisjiang@gmail.com Fixes: a3be076dc174 ("net/9p/usbg: Add new usb gadget function transport") Cc: stable@vger.kernel.org Message-ID: 20250622-9p-usb_overflow-v3-1-ab172691b946@codewreck.org Signed-off-by: Dominique Martinet asmadeus@codewreck.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/9p/trans_usbg.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
--- a/net/9p/trans_usbg.c +++ b/net/9p/trans_usbg.c @@ -231,6 +231,8 @@ static void usb9pfs_rx_complete(struct u struct f_usb9pfs *usb9pfs = ep->driver_data; struct usb_composite_dev *cdev = usb9pfs->function.config->cdev; struct p9_req_t *p9_rx_req; + unsigned int req_size = req->actual; + int status = REQ_STATUS_RCVD;
if (req->status) { dev_err(&cdev->gadget->dev, "%s usb9pfs complete --> %d, %d/%d\n", @@ -242,11 +244,19 @@ static void usb9pfs_rx_complete(struct u if (!p9_rx_req) return;
- memcpy(p9_rx_req->rc.sdata, req->buf, req->actual); + if (req_size > p9_rx_req->rc.capacity) { + dev_err(&cdev->gadget->dev, + "%s received data size %u exceeds buffer capacity %zu\n", + ep->name, req_size, p9_rx_req->rc.capacity); + req_size = 0; + status = REQ_STATUS_ERROR; + } + + memcpy(p9_rx_req->rc.sdata, req->buf, req_size);
- p9_rx_req->rc.size = req->actual; + p9_rx_req->rc.size = req_size;
- p9_client_cb(usb9pfs->client, p9_rx_req, REQ_STATUS_RCVD); + p9_client_cb(usb9pfs->client, p9_rx_req, status); p9_req_put(usb9pfs->client, p9_rx_req);
complete(&usb9pfs->received);