5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chunkai Deng commit 786439ad58763e04b91bc2ec5f590e463939f197 upstream. glink_smem_rx_peek() reads the RX FIFO payload after the caller has determined data is available via glink_smem_rx_avail(), which reads the remote-updated head index. A control dependency between the head read and the subsequent payload read does not order the two loads, so the CPU may speculatively read the FIFO before observing the head update and consume stale data the remote has not yet published. Add rmb() in glink_smem_rx_peek() before the memcpy_fromio() so the availability (head) read is ordered ahead of the FIFO payload read, matching the consumer pattern in Documentation/core-api/circular-buffers.rst. Fixes: caf989c350e8 ("rpmsg: glink: Introduce glink smem based transport") Cc: stable@vger.kernel.org Signed-off-by: Chunkai Deng Reviewed-by: Konrad Dybcio Link: https://lore.kernel.org/r/20260618-rpmsg-glink-smem-mb-v1-1-68a026453a69@oss.qualcomm.com Signed-off-by: Bjorn Andersson Signed-off-by: Greg Kroah-Hartman --- drivers/rpmsg/qcom_glink_smem.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/rpmsg/qcom_glink_smem.c +++ b/drivers/rpmsg/qcom_glink_smem.c @@ -88,6 +88,13 @@ static void glink_smem_rx_peak(struct qc if (tail >= pipe->native.length) tail -= pipe->native.length; + /* + * Order the availability (head) read in glink_smem_rx_avail() + * against the FIFO payload read below, so APPS never consumes + * stale data the remote has not yet published. + */ + rmb(); + len = min_t(size_t, count, pipe->native.length - tail); if (len) memcpy_fromio(data, pipe->fifo + tail, len);