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But the async DMA transfers issued by the > ring workers can still complete after the notification. And the completion > handlers trigger the client xfer_cb() as long as it is set. > > So a transfer completing during the flush can deliver a success callback to > the client even after it has been notified about the disconnect. This can > lead to UAF (Use-After-Free) issues as the client can free its per-transfer > resources in response to the -ENOTCONN notification and the trailing > success callback would then reference the freed resources. > > So to fix this issue, disable all the channels first to prevent new > transfers and then drain both the ring workqueue and the in-flight async > transfers before notifying the disconnect. The completion and queue paths > bail out once the channel state is not MHI_CH_STATE_RUNNING, so disabling > the channels upfront makes sure that no new transfer sneaks in during the > drain and all the pending completions are delivered while xfer_cb() is > still valid. > > Signed-off-by: Manivannan Sadhasivam > --- Reviewed-by: Frank Li > drivers/bus/mhi/ep/main.c | 23 +++++++++++++++++------ > 1 file changed, 17 insertions(+), 6 deletions(-) > > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c > index b94c571f01d8..51735f87017f 100644 > --- a/drivers/bus/mhi/ep/main.c > +++ b/drivers/bus/mhi/ep/main.c > @@ -1025,26 +1025,37 @@ static void mhi_ep_abort_transfer(struct mhi_ep_cntrl *mhi_cntrl) > struct mhi_ep_chan *mhi_chan; > int i; > > - /* Stop all the channels */ > + /* Disable all the channels to prevent new transfers */ > + for (i = 0; i < mhi_cntrl->max_chan; i++) { > + mhi_chan = &mhi_cntrl->mhi_chan[i]; > + if (!mhi_chan->ring.started) > + continue; > + > + mutex_lock(&mhi_chan->lock); > + mhi_chan->state = MHI_CH_STATE_DISABLED; > + mutex_unlock(&mhi_chan->lock); > + } > + > + /* Drain ring workers and in-flight transfers before notifying disconnect */ > + flush_workqueue(mhi_cntrl->wq); > + if (mhi_cntrl->flush_async) > + mhi_cntrl->flush_async(mhi_cntrl); > + > + /* Send channel disconnect status to client drivers */ > for (i = 0; i < mhi_cntrl->max_chan; i++) { > mhi_chan = &mhi_cntrl->mhi_chan[i]; > if (!mhi_chan->ring.started) > continue; > > mutex_lock(&mhi_chan->lock); > - /* Send channel disconnect status to client drivers */ > if (mhi_chan->xfer_cb) { > result.transaction_status = -ENOTCONN; > result.bytes_xferd = 0; > mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result); > } > - > - mhi_chan->state = MHI_CH_STATE_DISABLED; > mutex_unlock(&mhi_chan->lock); > } > > - flush_workqueue(mhi_cntrl->wq); > - > /* Destroy devices associated with all channels */ > device_for_each_child(&mhi_cntrl->mhi_dev->dev, NULL, mhi_ep_destroy_device); > > > -- > 2.43.0 > >