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

[Yunzhi Li]

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.
-- 
2.0.0


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