Re: [PATCH v1] usb: dwc2: gadget: fix a memory use-after-free bug

[John Youn]

On 5/28/2015 10:22 PM, Yunzhi Li wrote:
> When s3c_hsotg_handle_unaligned_buf_complete() hs_req->req.buf
> already destroyed, in s3c_hsotg_unmap_dma(), it touches
> hs_req->req.dma again, so s3c_hsotg_unmap_dma() should be called
> before s3c_hsotg_handle_unaligned_buf_complete(). Otherwise, it
> will cause a bad_page BUG, when allocate this memory page next
> time.
> 
> This bug led to the following crash:
> 
> BUG: Bad page state in process swapper/0  pfn:2bdbc
> [   26.820440] page:eed76780 count:0 mapcount:0 mapping:  (null) index:0x0
> [   26.854710] page flags: 0x200(arch_1)
> [   26.885836] page dumped because: PAGE_FLAGS_CHECK_AT_PREP flag set
> [   26.919179] bad because of flags:
> [   26.948917] page flags: 0x200(arch_1)
> [   26.979100] Modules linked in:
> [   27.008401] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W3.14.0 #17
> [   27.041816] [<c010e1f8>] (unwind_backtrace) from [<c010a704>] (show_stack+0x20/0x24)
> [   27.076108] [<c010a704>] (show_stack) from [<c087eea8>] (dump_stack+0x70/0x8c)
> [   27.110246] [<c087eea8>] (dump_stack) from [<c01ce0b8>] (bad_page+0xfc/0x12c)
> [   27.143958] [<c01ce0b8>] (bad_page) from [<c01ce65c>] (get_page_from_freelist+0x3e4/0x50c)
> [   27.179298] [<c01ce65c>] (get_page_from_freelist) from [<c01ce9a0>] (__alloc_pages_nodemask)
> [   27.216296] [<c01ce9a0>] (__alloc_pages_nodemask) from [<c01cf00c>] (__get_free_pages+0x20/)
> [   27.252326] [<c01cf00c>] (__get_free_pages) from [<c01e5bec>] (kmalloc_order_trace+0x34/0xa)
> [   27.288295] [<c01e5bec>] (kmalloc_order_trace) from [<c0203304>] (__kmalloc+0x40/0x1ac)
> [   27.323751] [<c0203304>] (__kmalloc) from [<c052abc0>] (s3c_hsotg_ep_queue.isra.12+0x7c/0x1)
> [   27.359937] [<c052abc0>] (s3c_hsotg_ep_queue.isra.12) from [<c052af88>] (s3c_hsotg_ep_queue)
> [   27.397478] [<c052af88>] (s3c_hsotg_ep_queue_lock) from [<c0554110>] (rx_submit+0xfc/0x164)
> [   27.433619] [<c0554110>] (rx_submit) from [<c05546e8>] (rx_complete+0x22c/0x230)
> [   27.468872] [<c05546e8>] (rx_complete) from [<c052b528>] (s3c_hsotg_complete_request+0xfc/0)
> [   27.506240] [<c052b528>] (s3c_hsotg_complete_request) from [<c052bba0>] (s3c_hsotg_handle_o)
> [   27.545401] [<c052bba0>] (s3c_hsotg_handle_outdone) from [<c052be70>] (s3c_hsotg_epint+0x2c)
> [   27.583689] [<c052be70>] (s3c_hsotg_epint) from [<c052c750>] (s3c_hsotg_irq+0x1dc/0x4ac)
> [   27.621041] [<c052c750>] (s3c_hsotg_irq) from [<c01682e0>] (handle_irq_event_percpu+0x70/0x)
> [   27.659066] [<c01682e0>] (handle_irq_event_percpu) from [<c01684ec>] (handle_irq_event+0x4c)
> [   27.697322] [<c01684ec>] (handle_irq_event) from [<c016bae0>] (handle_fasteoi_irq+0xc8/0x11)
> [   27.735451] [<c016bae0>] (handle_fasteoi_irq) from [<c0167b8c>] (generic_handle_irq+0x30/0x)
> [   27.773918] [<c0167b8c>] (generic_handle_irq) from [<c0167ca4>] (__handle_domain_irq+0x84/0)
> [   27.812018] [<c0167ca4>] (__handle_domain_irq) from [<c01003b0>] (gic_handle_irq+0x48/0x6c)
> [   27.849695] [<c01003b0>] (gic_handle_irq) from [<c010b340>] (__irq_svc+0x40/0x50)
> [   27.886907] Exception stack(0xc0d01ee0 to 0xc0d01f28)
> 
> Signed-off-by: Yunzhi Li <lyz@xxxxxxxxxxxxxx>
> 
> ---
> 
>  drivers/usb/dwc2/gadget.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> index 6a30887..8070602 100644
> --- a/drivers/usb/dwc2/gadget.c
> +++ b/drivers/usb/dwc2/gadget.c
> @@ -1389,14 +1389,14 @@ static void s3c_hsotg_complete_request(struct dwc2_hsotg *hsotg,
>  	if (hs_req->req.status == -EINPROGRESS)
>  		hs_req->req.status = result;
>  
> +	if (using_dma(hsotg))
> +		s3c_hsotg_unmap_dma(hsotg, hs_ep, hs_req);
> +
>  	s3c_hsotg_handle_unaligned_buf_complete(hsotg, hs_ep, hs_req);
>  
>  	hs_ep->req = NULL;
>  	list_del_init(&hs_req->queue);
>  
> -	if (using_dma(hsotg))
> -		s3c_hsotg_unmap_dma(hsotg, hs_ep, hs_req);
> -
>  	/*
>  	 * call the complete request with the locks off, just in case the
>  	 * request tries to queue more work for this endpoint.
> 


Acked-by: John Youn <johnyoun@xxxxxxxxxxxx>


John

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