Messages in this thread | | | Subject | Re: [PATCH v2] bus: mhi: core: Sanity check values from remote device before use | From | Jeffrey Hugo <> | Date | Wed, 24 Feb 2021 08:10:06 -0700 |
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On 2/24/2021 2:47 AM, Manivannan Sadhasivam wrote: > On Wed, Feb 17, 2021 at 09:20:22AM -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. >> 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@codeaurora.org> >> --- >> >> 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 c043574..1eb2fd3 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_device *mhi_dev; >> @@ -383,7 +388,16 @@ 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) >> @@ -536,6 +550,11 @@ 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); >> >> @@ -695,6 +714,12 @@ 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); >> @@ -719,6 +744,7 @@ 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 >> @@ -728,7 +754,13 @@ 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) { >> @@ -834,6 +866,8 @@ 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; > > This change is not part of this patch I believe.
It is. The remote device specified an event on a channel. We already check to see that the specified channel value doesn't exceed the maximum number of channels, but we don't check to see that it is a valid channel within the range of channels. If its not a valid channel (say 0-5 and 7-10 are valid, max is 10, but the remote end specified 6), bad things could happen because we are implicitly trusting the value before fully checking its validity.
This is still a sanity check of a value from the remote end.
-- Jeffrey Hugo Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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