Commit 6f18d174 authored by Sumit Kumar's avatar Sumit Kumar Committed by Manivannan Sadhasivam
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bus: mhi: ep: Update read pointer only after buffer is written 



Inside mhi_ep_ring_add_element, the read pointer (rd_offset) is updated
before the buffer is written, potentially causing race conditions where
the host sees an updated read pointer before the buffer is actually
written. Updating rd_offset prematurely can lead to the host accessing
an uninitialized or incomplete element, resulting in data corruption.

Invoke the buffer write before updating rd_offset to ensure the element
is fully written before signaling its availability.

Fixes: bbdcba57 ("bus: mhi: ep: Add support for ring management")
cc: stable@vger.kernel.org
Co-developed-by: default avatarYoussef Samir <quic_yabdulra@quicinc.com>
Signed-off-by: default avatarYoussef Samir <quic_yabdulra@quicinc.com>
Signed-off-by: default avatarSumit Kumar <quic_sumk@quicinc.com>
Reviewed-by: default avatarJeff Hugo <jeff.hugo@oss.qualcomm.com>
Reviewed-by: default avatarKrishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Reviewed-by: default avatarManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://patch.msgid.link/20250409-rp_fix-v1-1-8cf1fa22ed28@quicinc.com


Signed-off-by: default avatarManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
parent 0af2f6be

drivers/bus/mhi/ep/ring.c

+10 −6
Original line number Diff line number Diff line
@@ -131,19 +131,23 @@ int mhi_ep_ring_add_element(struct mhi_ep_ring *ring, struct mhi_ring_element *e 
	}



	old_offset = ring->rd_offset;

	mhi_ep_ring_inc_index(ring);



	dev_dbg(dev, "Adding an element to ring at offset (%zu)\n", ring->rd_offset);

	buf_info.host_addr = ring->rbase + (old_offset * sizeof(*el));

	buf_info.dev_addr = el;

	buf_info.size = sizeof(*el);



	ret = mhi_cntrl->write_sync(mhi_cntrl, &buf_info);

	if (ret)

		return ret;



	mhi_ep_ring_inc_index(ring);



	/* Update rp in ring context */

	rp = cpu_to_le64(ring->rd_offset * sizeof(*el) + ring->rbase);

	memcpy_toio((void __iomem *) &ring->ring_ctx->generic.rp, &rp, sizeof(u64));



	buf_info.host_addr = ring->rbase + (old_offset * sizeof(*el));

	buf_info.dev_addr = el;

	buf_info.size = sizeof(*el);



	return mhi_cntrl->write_sync(mhi_cntrl, &buf_info);

	return ret;

}



void mhi_ep_ring_init(struct mhi_ep_ring *ring, enum mhi_ep_ring_type type, u32 id)