6.6-stable review patch. If anyone has any objections, please let me know.
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From: Michal Pecio michal.pecio@gmail.com
commit 1ea050da5562af9b930d17cbbe9632d30f5df43a upstream.
This check is performed before prepare_transfer() and prepare_ring(), so enqueue can already point at the final link TRB of a segment. And indeed it will, some 0.4% of times this code is called.
Then enqueue + 1 is an invalid pointer. It will crash the kernel right away or load some junk which may look like a link TRB and cause the real link TRB to be replaced with a NOOP. This wouldn't end well.
Use a functionally equivalent test which doesn't dereference the pointer and always gives correct result.
Something has crashed my machine twice in recent days while playing with an Etron HC, and a control transfer stress test ran for confirmation has just crashed it again. The same test passes with this patch applied.
Fixes: 5e1c67abc930 ("xhci: Fix control transfer error on Etron xHCI host") Cc: stable@vger.kernel.org Signed-off-by: Michal Pecio michal.pecio@gmail.com Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Reviewed-by: Kuangyi Chiang ki.chiang65@gmail.com Link: https://lore.kernel.org/r/20250410151828.2868740-5-mathias.nyman@linux.intel... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/host/xhci-ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -3876,7 +3876,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd * * enqueue a No Op TRB, this can prevent the Setup and Data Stage * TRB to be breaked by the Link TRB. */ - if (trb_is_link(ep_ring->enqueue + 1)) { + if (last_trb_on_seg(ep_ring->enq_seg, ep_ring->enqueue + 1)) { field = TRB_TYPE(TRB_TR_NOOP) | ep_ring->cycle_state; queue_trb(xhci, ep_ring, false, 0, 0, TRB_INTR_TARGET(0), field);