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: bbdcba57a1a2 ("bus: mhi: ep: Add support for ring management") cc: stable@vger.kernel.org Co-developed-by: Youssef Samir quic_yabdulra@quicinc.com Signed-off-by: Youssef Samir quic_yabdulra@quicinc.com Signed-off-by: Sumit Kumar quic_sumk@quicinc.com --- drivers/bus/mhi/ep/ring.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/bus/mhi/ep/ring.c b/drivers/bus/mhi/ep/ring.c index aeb53b2c34a8cd859393529d0c8860462bc687ed..26357ee68dee984d70ae5bf39f8f09f2cbcafe30 100644 --- a/drivers/bus/mhi/ep/ring.c +++ b/drivers/bus/mhi/ep/ring.c @@ -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)

--- base-commit: 1e26c5e28ca5821a824e90dd359556f5e9e7b89f change-id: 20250328-rp_fix-d7ebc18bc3be

Best regards,