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* [PATCH] bus: mhi: host: Fix race between channel preparation and M0 event
@ 2022-10-10  4:53 Qiang Yu
  0 siblings, 0 replies; only message in thread
From: Qiang Yu @ 2022-10-10  4:53 UTC (permalink / raw)
  To: mani, quic_hemantk, loic.poulain
  Cc: mhi, linux-arm-msm, linux-kernel, quic_cang, mrana, Qiang Yu

There is a race condition where mhi_prepare_channel() updates the
read and write pointers as the base address and in parallel, if
an M0 transition occurs, the tasklet goes ahead and rings
doorbells for all channels with a delta in TRE rings assuming
they are already enabled. This causes a null pointer access. Fix
it by adding a channel enabled check before ringing channel

Signed-off-by: Qiang Yu <>
 drivers/bus/mhi/host/pm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
index 4a42186..0834590 100644
--- a/drivers/bus/mhi/host/pm.c
+++ b/drivers/bus/mhi/host/pm.c
@@ -301,7 +301,8 @@ int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl)
 		/* Only ring DB if ring is not empty */
-		if (tre_ring->base && tre_ring->wp  != tre_ring->rp)
+		if (tre_ring->base && tre_ring->wp  != tre_ring->rp &&
+		    mhi_chan->ch_state == MHI_CH_STATE_ENABLED)
 			mhi_ring_chan_db(mhi_cntrl, mhi_chan);
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a Linux Foundation Collaborative Project

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2022-10-10  4:53 [PATCH] bus: mhi: host: Fix race between channel preparation and M0 event Qiang Yu

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