From 18f08bf8df95c687d6fee3d2bb747cbd2fa0b878 Mon Sep 17 00:00:00 2001 From: Jonathan Bell Date: Thu, 22 Sep 2022 14:55:54 +0100 Subject: [PATCH] usb: xhci: account for num_trbs_free when invalidating TDs If a ring has a number of TDs enqueued past the dequeue pointer, and the URBs corresponding to these TDs are dequeued, then num_trbs_free isn't updated to show that these TDs have been converted to no-ops and effectively "freed". This means that num_trbs_free creeps downwards until the count is exhausted, which then triggers xhci_ring_expansion() and effectively leaks memory by infinitely growing the transfer ring. This is commonly encounted through the use of a usb-serial port where the port is repeatedly opened, read, then closed. Move the num_trbs_free crediting out of the Set TR Dequeue Pointer handling and into xhci_invalidate_cancelled_tds(). There is a potential for overestimating the actual space on the ring if the ring is nearly full and TDs are arbitrarily enqueued by a device driver while it is dequeueing them, but dequeues are usually batched during device close/shutdown or endpoint error recovery. See https://github.com/raspberrypi/linux/issues/5088 Signed-off-by: Jonathan Bell --- drivers/usb/host/xhci-ring.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1012,11 +1012,13 @@ static int xhci_invalidate_cancelled_tds td->urb->stream_id, td->urb, cached_td->urb->stream_id, cached_td->urb); cached_td = td; + ring->num_trbs_free += td->num_trbs; break; } } else { td_to_noop(xhci, ring, td, false); td->cancel_status = TD_CLEARED; + ring->num_trbs_free += td->num_trbs; } } @@ -1264,10 +1266,7 @@ static void update_ring_for_set_deq_comp unsigned int ep_index) { union xhci_trb *dequeue_temp; - int num_trbs_free_temp; - bool revert = false; - num_trbs_free_temp = ep_ring->num_trbs_free; dequeue_temp = ep_ring->dequeue; /* If we get two back-to-back stalls, and the first stalled transfer @@ -1282,8 +1281,6 @@ static void update_ring_for_set_deq_comp } while (ep_ring->dequeue != dev->eps[ep_index].queued_deq_ptr) { - /* We have more usable TRBs */ - ep_ring->num_trbs_free++; ep_ring->dequeue++; if (trb_is_link(ep_ring->dequeue)) { if (ep_ring->dequeue == @@ -1293,15 +1290,10 @@ static void update_ring_for_set_deq_comp ep_ring->dequeue = ep_ring->deq_seg->trbs; } if (ep_ring->dequeue == dequeue_temp) { - revert = true; + xhci_dbg(xhci, "Unable to find new dequeue pointer\n"); break; } } - - if (revert) { - xhci_dbg(xhci, "Unable to find new dequeue pointer\n"); - ep_ring->num_trbs_free = num_trbs_free_temp; - } } /*