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Date: Wed, 7 Apr 2021 13:51:50 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Jeffrey Hugo <jhugo@...eaurora.org>
Cc: hemantk@...eaurora.org, bbhatt@...eaurora.org,
linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] bus: mhi: core: Sanity check values from remote
device before use
On Wed, Mar 10, 2021 at 02:30:55PM -0700, Jeffrey Hugo wrote:
> When parsing the structures in the shared memory, there are values which
> come from the remote device. For example, a transfer completion event
> will have a pointer to the tre in the relevant channel's transfer ring.
> As another example, event ring elements may specify a channel in which
> the event occurred, however the specified channel value may not be valid
> as no channel is defined at that index even though the index may be less
> than the maximum allowed index. Such values should be considered to be
> untrusted, and validated before use. If we blindly use such values, we
> may access invalid data or crash if the values are corrupted.
>
> If validation fails, drop the relevant event.
>
> Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
Looks good to me, but I need an ACK from Hemant/Bhaumik.
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Thanks,
Mani
> ---
>
> v3: Add the channel validation example to commit text
> v2: Fix subject
>
> drivers/bus/mhi/core/main.c | 81 +++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 74 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index a7811fb..6c0e05d 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -242,6 +242,11 @@ static void mhi_del_ring_element(struct mhi_controller *mhi_cntrl,
> smp_wmb();
> }
>
> +static bool is_valid_ring_ptr(struct mhi_ring *ring, dma_addr_t addr)
> +{
> + return addr >= ring->iommu_base && addr < ring->iommu_base + ring->len;
> +}
> +
> int mhi_destroy_device(struct device *dev, void *data)
> {
> struct mhi_chan *ul_chan, *dl_chan;
> @@ -404,7 +409,16 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
> struct mhi_event_ctxt *er_ctxt =
> &mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
> struct mhi_ring *ev_ring = &mhi_event->ring;
> - void *dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> + dma_addr_t ptr = er_ctxt->rp;
> + void *dev_rp;
> +
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + return IRQ_HANDLED;
> + }
> +
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
>
> /* Only proceed if event ring has pending events */
> if (ev_ring->rp == dev_rp)
> @@ -560,6 +574,11 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
> struct mhi_buf_info *buf_info;
> u16 xfer_len;
>
> + if (!is_valid_ring_ptr(tre_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event element points outside of the tre ring\n");
> + break;
> + }
> /* Get the TRB this event points to */
> ev_tre = mhi_to_virtual(tre_ring, ptr);
>
> @@ -719,6 +738,12 @@ static void mhi_process_cmd_completion(struct mhi_controller *mhi_cntrl,
> struct mhi_chan *mhi_chan;
> u32 chan;
>
> + if (!is_valid_ring_ptr(mhi_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event element points outside of the cmd ring\n");
> + return;
> + }
> +
> cmd_pkt = mhi_to_virtual(mhi_ring, ptr);
>
> chan = MHI_TRE_GET_CMD_CHID(cmd_pkt);
> @@ -743,6 +768,7 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
> struct device *dev = &mhi_cntrl->mhi_dev->dev;
> u32 chan;
> int count = 0;
> + dma_addr_t ptr = er_ctxt->rp;
>
> /*
> * This is a quick check to avoid unnecessary event processing
> @@ -752,7 +778,13 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
> if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
> return -EIO;
>
> - dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + return -EIO;
> + }
> +
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
> local_rp = ev_ring->rp;
>
> while (dev_rp != local_rp) {
> @@ -858,6 +890,8 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
> */
> if (chan < mhi_cntrl->max_chan) {
> mhi_chan = &mhi_cntrl->mhi_chan[chan];
> + if (!mhi_chan->configured)
> + break;
> parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
> event_quota--;
> }
> @@ -869,7 +903,15 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>
> mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
> local_rp = ev_ring->rp;
> - dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> + ptr = er_ctxt->rp;
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + return -EIO;
> + }
> +
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
> count++;
> }
>
> @@ -892,11 +934,18 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
> int count = 0;
> u32 chan;
> struct mhi_chan *mhi_chan;
> + dma_addr_t ptr = er_ctxt->rp;
>
> if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
> return -EIO;
>
> - dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + return -EIO;
> + }
> +
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
> local_rp = ev_ring->rp;
>
> while (dev_rp != local_rp && event_quota > 0) {
> @@ -910,7 +959,8 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
> * Only process the event ring elements whose channel
> * ID is within the maximum supported range.
> */
> - if (chan < mhi_cntrl->max_chan) {
> + if (chan < mhi_cntrl->max_chan &&
> + mhi_cntrl->mhi_chan[chan].configured) {
> mhi_chan = &mhi_cntrl->mhi_chan[chan];
>
> if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
> @@ -924,7 +974,15 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>
> mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
> local_rp = ev_ring->rp;
> - dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> + ptr = er_ctxt->rp;
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + return -EIO;
> + }
> +
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
> count++;
> }
> read_lock_bh(&mhi_cntrl->pm_lock);
> @@ -1385,6 +1443,7 @@ static void mhi_mark_stale_events(struct mhi_controller *mhi_cntrl,
> struct mhi_ring *ev_ring;
> struct device *dev = &mhi_cntrl->mhi_dev->dev;
> unsigned long flags;
> + dma_addr_t ptr;
>
> dev_dbg(dev, "Marking all events for chan: %d as stale\n", chan);
>
> @@ -1392,7 +1451,15 @@ static void mhi_mark_stale_events(struct mhi_controller *mhi_cntrl,
>
> /* mark all stale events related to channel as STALE event */
> spin_lock_irqsave(&mhi_event->lock, flags);
> - dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> + ptr = er_ctxt->rp;
> + if (!is_valid_ring_ptr(ev_ring, ptr)) {
> + dev_err(&mhi_cntrl->mhi_dev->dev,
> + "Event ring rp points outside of the event ring\n");
> + dev_rp = ev_ring->rp;
> + } else {
> + dev_rp = mhi_to_virtual(ev_ring, ptr);
> + }
>
> local_rp = ev_ring->rp;
> while (dev_rp != local_rp) {
> --
> Qualcomm Technologies, Inc. is a member of the
> Code Aurora Forum, a Linux Foundation Collaborative Project.
>
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