USB: EHCI: AMD periodic frame list table quirk

On AMD SB700/SB800/Hudson-2/3 platforms, USB EHCI controller may read/write
to memory space not allocated to USB controller if there is longer than
normal latency on DMA read encountered. In this condition the exposure will
be encountered only if the driver has following format of Periodic Frame
List link pointer structure:

For any idle periodic schedule, the Frame List link pointers that have the
T-bit set to 1 intending to terminate the use of frame list link pointer
as a physical memory pointer.

Idle periodic schedule Frame List Link pointer shoule be in the following
format to avoid the issue:

Frame list link pointer should be always contains a valid pointer to a
inactive QHead with T-bit set to 0.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index a92526d6e5ae..d9f78eb26572 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -98,7 +98,14 @@ static void periodic_unlink (struct ehci_hcd *ehci, unsigned frame, void *ptr)
          */
         *prev_p = *periodic_next_shadow(ehci, &here,
                         Q_NEXT_TYPE(ehci, *hw_p));
-        *hw_p = *shadow_next_periodic(ehci, &here, Q_NEXT_TYPE(ehci, *hw_p));
+
+        if (!ehci->use_dummy_qh ||
+            *shadow_next_periodic(ehci, &here, Q_NEXT_TYPE(ehci, *hw_p))
+                        != EHCI_LIST_END(ehci))
+                *hw_p = *shadow_next_periodic(ehci, &here,
+                                Q_NEXT_TYPE(ehci, *hw_p));
+        else
+                *hw_p = ehci->dummy->qh_dma;
 }
 
 /* how many of the uframe's 125 usecs are allocated? */
@@ -2335,7 +2342,11 @@ restart:
                                  * pointer for much longer, if at all.
                                  */
                                 *q_p = q.itd->itd_next;
-                                *hw_p = q.itd->hw_next;
+                                if (!ehci->use_dummy_qh ||
+                                    q.itd->hw_next != EHCI_LIST_END(ehci))
+                                        *hw_p = q.itd->hw_next;
+                                else
+                                        *hw_p = ehci->dummy->qh_dma;
                                 type = Q_NEXT_TYPE(ehci, q.itd->hw_next);
                                 wmb();
                                 modified = itd_complete (ehci, q.itd);
@@ -2368,7 +2379,11 @@ restart:
                                  * URB completion.
                                  */
                                 *q_p = q.sitd->sitd_next;
-                                *hw_p = q.sitd->hw_next;
+                                if (!ehci->use_dummy_qh ||
+                                    q.sitd->hw_next != EHCI_LIST_END(ehci))
+                                        *hw_p = q.sitd->hw_next;
+                                else
+                                        *hw_p = ehci->dummy->qh_dma;
                                 type = Q_NEXT_TYPE(ehci, q.sitd->hw_next);
                                 wmb();
                                 modified = sitd_complete (ehci, q.sitd);