[Qemu-devel] [PATCH v2] usb: fix unbounded stack warning for xhci_dma_write_u32s

[Qemu-devel] [PATCH v2] usb: fix unbounded stack warning for xhci_dma_write_u32s

[Peter Xu]

All the callers for xhci_dma_write_u32s() are using mostly 5 * uint32_t
in len. To avoid unbound stack warning for the function, make it
statically allocated, and assert when it's not big enough in the
future.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 hw/usb/hcd-xhci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index 44b6f8c..bcde8a2 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -698,11 +698,13 @@ static inline void xhci_dma_write_u32s(XHCIState *xhci, dma_addr_t addr,
                                        uint32_t *buf, size_t len)
 {
     int i;
-    uint32_t tmp[len / sizeof(uint32_t)];
+    uint32_t tmp[5];
+    uint32_t n = len / sizeof(uint32_t);
 
     assert((len % sizeof(uint32_t)) == 0);
+    assert(n <= ARRAY_SIZE(tmp));
 
-    for (i = 0; i < (len / sizeof(uint32_t)); i++) {
+    for (i = 0; i < n; i++) {
         tmp[i] = cpu_to_le32(buf[i]);
     }
     pci_dma_write(PCI_DEVICE(xhci), addr, tmp, len);
-- 
2.4.3

Re: [Qemu-devel] [PATCH v2] usb: fix unbounded stack warning for xhci_dma_write_u32s

[Gerd Hoffmann]

On Fr, 2016-03-11 at 09:51 +0800, Peter Xu wrote:
> All the callers for xhci_dma_write_u32s() are using mostly 5 * uint32_t
> in len. To avoid unbound stack warning for the function, make it
> statically allocated, and assert when it's not big enough in the
> future.

Added to usb queue.

thanks,
  Gerd