usb: core: buffer: avoid NULL pointer dereferrence

NULL pointer dereferrence will happen when class driver
wants to allocate zero length buffer and pool_max[0]
can't be used, so simply returns NULL in the case.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/buffer.c b/drivers/usb/core/buffer.c
index 2741566..98e39f9 100644 (file)
--- a/drivers/usb/core/buffer.c
+++ b/drivers/usb/core/buffer.c
@@ -122,6 +122,9 @@ void *hcd_buffer_alloc(
        struct usb_hcd          *hcd = bus_to_hcd(bus);
        int                     i;
 
+       if (size == 0)
+               return NULL;
+
        /* some USB hosts just use PIO */
        if (!IS_ENABLED(CONFIG_HAS_DMA) ||
            (!bus->controller->dma_mask &&