bus: mhi: host: Drop chan lock before queuing buffers

commit 01bd694ac2f682fb8017e16148b928482bc8fa4b upstream.

Ensure read and write locks for the channel are not taken in succession by
dropping the read lock from parse_xfer_event() such that a callback given
to client can potentially queue buffers and acquire the write lock in that
process. Any queueing of buffers should be done without channel read lock
acquired as it can result in multiple locks and a soft lockup.

Cc: <stable@vger.kernel.org> # 5.7
Fixes: 1d3173a3bae7 ("bus: mhi: core: Add support for processing events from client device")
Signed-off-by: Qiang Yu <quic_qianyu@quicinc.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Tested-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1702276972-41296-3-git-send-email-quic_qianyu@quicinc.com
[mani: added fixes tag and cc'ed stable]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 3a6ccab..25a4745 100644 (file)
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -643,6 +643,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
                        mhi_del_ring_element(mhi_cntrl, tre_ring);
                        local_rp = tre_ring->rp;
 
+                       read_unlock_bh(&mhi_chan->lock);
+
                        /* notify client */
                        mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
 
@@ -668,6 +670,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
                                        kfree(buf_info->cb_buf);
                                }
                        }
+
+                       read_lock_bh(&mhi_chan->lock);
                }
                break;
        } /* CC_EOT */