usb: dwc3: gadget: Fix looping of queued SG entries

The dwc3_request->num_queued_sgs is decremented on completion. If a
partially completed request is handled, then the
dwc3_request->num_queued_sgs no longer reflects the total number of
num_queued_sgs (it would be cleared).

Correctly check the number of request SG entries remained to be prepare
and queued. Failure to do this may cause null pointer dereference when
accessing non-existent SG entry.

Cc: stable@vger.kernel.org
Fixes: c96e6725db9d ("usb: dwc3: gadget: Correct the logic for queuing sgs")
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/d07a7c4aa0fcf746cdca0515150dbe5c52000af7.1731545781.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 38c3769a6c480a8aba79581e01566614053b8ce7..3a5a0d8be33c049736966c5b947b9cbbc777af7f 100644 (file)
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1470,8 +1470,8 @@ static int dwc3_prepare_trbs_sg(struct dwc3_ep *dep,
        struct scatterlist *s;
        int             i;
        unsigned int length = req->request.length;
-       unsigned int remaining = req->request.num_mapped_sgs
-               - req->num_queued_sgs;
+       unsigned int remaining = req->num_pending_sgs;
+       unsigned int num_queued_sgs = req->request.num_mapped_sgs - remaining;
        unsigned int num_trbs = req->num_trbs;
        bool needs_extra_trb = dwc3_needs_extra_trb(dep, req);
 
@@ -1479,7 +1479,7 @@ static int dwc3_prepare_trbs_sg(struct dwc3_ep *dep,
         * If we resume preparing the request, then get the remaining length of
         * the request and resume where we left off.
         */
-       for_each_sg(req->request.sg, s, req->num_queued_sgs, i)
+       for_each_sg(req->request.sg, s, num_queued_sgs, i)
                length -= sg_dma_len(s);
 
        for_each_sg(sg, s, remaining, i) {