Re: [PATCH] mtk-sd: Prevent memory corruption from DMA map failure
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2025-06-19 02:05:05
Also in:
linux-mediatek, linux-mmc, lkml
Ping? I think there will be another bug which leaks the resources to cause this failure case. But anyway, without this fix, if DMA preparation fails but runs a DMA, it will overwrite the previous read buffer memory. Thank you, On Thu, 12 Jun 2025 20:26:10 +0900 "Masami Hiramatsu (Google)" [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> If msdc_prepare_data() fails to map the DMA region, the request is not prepared for data receiving, but msdc_start_data() proceeds the DMA with previous setting. Since this will lead a memory corruption, we have to stop the request operation soon after the msdc_prepare_data() fails to prepare it. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- drivers/mmc/host/mtk-sd.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c index 3594010bc229..56b4999fe58f 100644 --- a/drivers/mmc/host/mtk-sd.c +++ b/drivers/mmc/host/mtk-sd.c@@ -834,6 +834,11 @@ static void msdc_prepare_data(struct msdc_host *host, struct mmc_data *data) } } +static bool msdc_data_prepared(struct mmc_data *data) +{ + return data->host_cookie & MSDC_PREPARE_FLAG; +} + static void msdc_unprepare_data(struct msdc_host *host, struct mmc_data *data) { if (data->host_cookie & MSDC_ASYNC_FLAG)@@ -1466,8 +1471,18 @@ static void msdc_ops_request(struct mmc_host *mmc, struct mmc_request *mrq) WARN_ON(!host->hsq_en && host->mrq); host->mrq = mrq; - if (mrq->data) + if (mrq->data) { msdc_prepare_data(host, mrq->data); + if (!msdc_data_prepared(mrq->data)) { + /* + * Failed to prepare DMA area, fail fast before + * starting any commands. + */ + mrq->cmd->error = -ENOSPC; + mmc_request_done(mmc_from_priv(host), mrq); + return; + } + } /* if SBC is required, we have HW option and SW option. * if HW option is enabled, and SBC does not have "special" flags,
-- Masami Hiramatsu (Google) [off-list ref]