Polling mode transactions wait for a reply busy-looping without holding a spinlock, but currently the timeout checks are based only on elapsed time: as a result we could hit a false positive whenever our busy-looping thread is pre-empted and scheduled out for a time greater than the polling timeout.

Change the checks at the end of the busy-loop to make sure that the polling wasn't indeed successful or an out-of-order reply caused the polling to be forcibly terminated.

Fixes: 31d2f803c19c ("firmware: arm_scmi: Add sync_cmds_completed_on_ret transport flag") Reported-by: Huangjie huangjie1663@phytium.com.cn Closes: https://lore.kernel.org/arm-scmi/20250123083323.2363749-1-jackhuang021@gmail... Signed-off-by: Cristian Marussi cristian.marussi@arm.com Cc: stable@vger.kernel.org # 5.18.x --- This fix got to be backported to 5.4/5.10./5.15 due to small changes in the context --- drivers/firmware/arm_scmi/driver.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c index 60050da54bf2..e6cf83950875 100644 --- a/drivers/firmware/arm_scmi/driver.c +++ b/drivers/firmware/arm_scmi/driver.c @@ -1248,7 +1248,8 @@ static void xfer_put(const struct scmi_protocol_handle *ph, }

static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo, - struct scmi_xfer *xfer, ktime_t stop) + struct scmi_xfer *xfer, ktime_t stop, + bool *ooo) { struct scmi_info *info = handle_to_scmi_info(cinfo->handle);

@@ -1257,7 +1258,7 @@ static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo, * in case of out-of-order receptions of delayed responses */ return info->desc->ops->poll_done(cinfo, xfer) || - try_wait_for_completion(&xfer->done) || + (*ooo = try_wait_for_completion(&xfer->done)) || ktime_after(ktime_get(), stop); }

@@ -1274,15 +1275,17 @@ static int scmi_wait_for_reply(struct device *dev, const struct scmi_desc *desc, * itself to support synchronous commands replies. */ if (!desc->sync_cmds_completed_on_ret) { + bool ooo = false; + /* * Poll on xfer using transport provided .poll_done(); * assumes no completion interrupt was available. */ ktime_t stop = ktime_add_ms(ktime_get(), timeout_ms);

- spin_until_cond(scmi_xfer_done_no_timeout(cinfo, - xfer, stop)); - if (ktime_after(ktime_get(), stop)) { + spin_until_cond(scmi_xfer_done_no_timeout(cinfo, xfer, + stop, &ooo)); + if (!ooo && !info->desc->ops->poll_done(cinfo, xfer)) { dev_err(dev, "timed out in resp(caller: %pS) - polling\n", (void *)_RET_IP_);