6.6-stable review patch. If anyone has any objections, please let me know.
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From: Sumit Kumar quic_sumk@quicinc.com
commit 6f18d174b73d0ceeaa341f46c0986436b3aefc9a upstream.
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 Reviewed-by: Jeff Hugo jeff.hugo@oss.qualcomm.com Reviewed-by: Krishna Chaitanya Chundru krishna.chundru@oss.qualcomm.com Reviewed-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Link: https://patch.msgid.link/20250409-rp_fix-v1-1-8cf1fa22ed28@quicinc.com Signed-off-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/bus/mhi/ep/ring.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
--- 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_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)