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mtk-sd: Fix a pagefault in dma_unmap_sg() for not prepared data

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commit 539d80575b810c7a5987c7ac8915e3bc99c03695 upstream.

When swiotlb buffer is full, the dma_map_sg() returns 0 to
msdc_prepare_data(), but it does not check it and sets the
MSDC_PREPARE_FLAG.

swiotlb_tbl_map_single() /* prints "swiotlb buffer is full" */
  <-swiotlb_map()
    <-dma_direct_map_page()
      <-dma_direct_map_sg()
        <-__dma_map_sg_attrs()
          <-dma_map_sg_attrs()
            <-dma_map_sg()  /* returns 0 (pages mapped) */
              <-msdc_prepare_data()

Then, the msdc_unprepare_data() checks MSDC_PREPARE_FLAG and calls
dma_unmap_sg() with unmapped pages. It causes a page fault.

To fix this problem, Do not set MSDC_PREPARE_FLAG if dma_map_sg()
fails because this is not prepared.

Fixes: 208489032b ("mmc: mediatek: Add Mediatek MMC driver")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/174908565814.4056588.769599127120955383.stgit@mhiramat.tok.corp.google.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Masami Hiramatsu (Google) 2025-06-05 10:07:38 +09:00 • committed by Greg Kroah-Hartman
commit 35fcc9ea84
1 changed files with 2 additions and 1 deletions
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3
drivers/mmc/host/mtk-sd.c
View file

@ -681,9 +681,10 @@ static void msdc_prepare_data(struct msdc_host *host, struct mmc_request *mrq)
struct mmc_data *data = mrq->data;
if (!(data->host_cookie & MSDC_PREPARE_FLAG)) {
data->host_cookie |= MSDC_PREPARE_FLAG;
data->sg_count = dma_map_sg(host->dev, data->sg, data->sg_len,
mmc_get_dma_dir(data));
if (data->sg_count)
data->host_cookie |= MSDC_PREPARE_FLAG;
}
}