| Message ID | 20250317222927.5b76518e@foxbook |
|---|---|
| State | New |
| Headers | show |
| Series | usb: xhci: Fix invalid pointer dereference in Etron workaround | expand |
Hi, Michal Pecio <michal.pecio@gmail.com> 於 2025年3月18日 週二 上午5:29寫道： > > 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. Ah, this could happen, my bad. > > 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> > --- > drivers/usb/host/xhci-ring.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c > index 60d89cf418da..dc674bc24a89 100644 > --- a/drivers/usb/host/xhci-ring.c > +++ b/drivers/usb/host/xhci-ring.c > @@ -3786,7 +3786,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags, > * 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); > -- > 2.48.1 Reviewed-by: Kuangyi Chiang <ki.chiang65@gmail.com> Thanks for the patch, Kuangyi Chiang
Hi Mathias, Gentle reminder about a pretty annoying bug, it would seem like a good idea to have it fixed in 6.15-rc2. Basically, if you use SS control transfers on Etron, this happens: [88483.258966] xhci_hcd 0000:06:00.0: last TRB on seg we're gonna dieee!!! [88483.260825] BUG: unable to handle page fault for address: ffffc9000177a00c [88483.262441] #PF: supervisor read access in kernel mode [88483.263889] #PF: error_code(0x0000) - not-present page [88483.265306] PGD 100000067 P4D 100000067 PUD 100234067 PMD 103dd4067 PTE 0 [88483.266648] Oops: Oops: 0000 [#1] SMP [88483.267980] CPU: 2 UID: 1000 PID: 20753 Comm: v4l2-ctl Not tainted 6.15.0-rc1 #7 PREEMPT [88483.269327] Hardware name: HP HP EliteDesk 705 G3 MT/8265, BIOS P06 Ver. 02.45 07/16/2024 [88483.270689] RIP: 0010:xhci_queue_ctrl_tx+0xaf/0x410 [xhci_hcd] On Mon, 17 Mar 2025 22:29:27 +0100, Michal Pecio wrote: > 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> Regards, Michal
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 60d89cf418da..dc674bc24a89 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -3786,7 +3786,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags, * 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);
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> --- drivers/usb/host/xhci-ring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)