From f8324611c1ec100fd601842d3943cbf8acd1420f Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 24 Aug 2023 17:48:18 +0100 Subject: [PATCH] hw/usb/hcd-xhci: Avoid variable-length array in xhci_get_port_bandwidth() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit In xhci_get_port_bandwidth(), we use a variable-length array to construct the buffer to send back to the guest. Avoid the VLA by using dma_memory_set() to directly request the memory system to fill the guest memory with a string of '80's. The codebase has very few VLAs, and if we can get rid of them all we can make the compiler error on new additions. This is a defensive measure against security bugs where an on-stack dynamic allocation isn't correctly size-checked (e.g. CVE-2021-3527). Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Philippe Mathieu-Daudé Message-ID: <20230824164818.2652452-1-peter.maydell@linaro.org> --- hw/usb/hcd-xhci.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c index b89b618ec2..324177ad5d 100644 --- a/hw/usb/hcd-xhci.c +++ b/hw/usb/hcd-xhci.c @@ -2434,7 +2434,6 @@ static void xhci_detach_slot(XHCIState *xhci, USBPort *uport) static TRBCCode xhci_get_port_bandwidth(XHCIState *xhci, uint64_t pctx) { dma_addr_t ctx; - uint8_t bw_ctx[xhci->numports+1]; DPRINTF("xhci_get_port_bandwidth()\n"); @@ -2442,11 +2441,10 @@ static TRBCCode xhci_get_port_bandwidth(XHCIState *xhci, uint64_t pctx) DPRINTF("xhci: bandwidth context at "DMA_ADDR_FMT"\n", ctx); - /* TODO: actually implement real values here */ - bw_ctx[0] = 0; - memset(&bw_ctx[1], 80, xhci->numports); /* 80% */ - if (dma_memory_write(xhci->as, ctx, bw_ctx, sizeof(bw_ctx), - MEMTXATTRS_UNSPECIFIED) != MEMTX_OK) { + /* TODO: actually implement real values here. This is 80% for all ports. */ + if (stb_dma(xhci->as, ctx, 0, MEMTXATTRS_UNSPECIFIED) != MEMTX_OK || + dma_memory_set(xhci->as, ctx + 1, 80, xhci->numports, + MEMTXATTRS_UNSPECIFIED) != MEMTX_OK) { qemu_log_mask(LOG_GUEST_ERROR, "%s: DMA memory write failed!\n", __func__); return CC_TRB_ERROR; -- 2.39.5