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    Subject[PATCH v3 2/9] drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_generic_write_seq()
    Date
    The mipi_dsi_generic_write_seq() macro makes a call to
    mipi_dsi_generic_write() which returns a type ssize_t. The macro then
    stores it in an int and checks to see if it's negative. This could
    theoretically be a problem if "ssize_t" is larger than "int".

    To see the issue, imagine that "ssize_t" is 32-bits and "int" is
    16-bits, you could see a problem if there was some code out there that
    looked like:

    mipi_dsi_generic_write_seq(dsi, <32768 bytes as arguments>);

    ..since we'd get back that 32768 bytes were transferred and 32768
    stored in a 16-bit int would look negative.

    Though there are no callsites where we'd actually hit this (even if
    "int" was only 16-bit), it's cleaner to make the types match so let's
    fix it.

    Fixes: a9015ce59320 ("drm/mipi-dsi: Add a mipi_dsi_dcs_write_seq() macro")
    Signed-off-by: Douglas Anderson <dianders@chromium.org>
    ---

    Changes in v3:
    - Use %zd in print instead of casting errors to int.

    Changes in v2:
    - New

    include/drm/drm_mipi_dsi.h | 22 +++++++++++-----------
    1 file changed, 11 insertions(+), 11 deletions(-)

    diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
    index 70ce0b8cbc68..e0f56564bf97 100644
    --- a/include/drm/drm_mipi_dsi.h
    +++ b/include/drm/drm_mipi_dsi.h
    @@ -314,17 +314,17 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
    * @dsi: DSI peripheral device
    * @seq: buffer containing the payload
    */
    -#define mipi_dsi_generic_write_seq(dsi, seq...) \
    - do { \
    - static const u8 d[] = { seq }; \
    - struct device *dev = &dsi->dev; \
    - int ret; \
    - ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d)); \
    - if (ret < 0) { \
    - dev_err_ratelimited(dev, "transmit data failed: %d\n", \
    - ret); \
    - return ret; \
    - } \
    +#define mipi_dsi_generic_write_seq(dsi, seq...) \
    + do { \
    + static const u8 d[] = { seq }; \
    + struct device *dev = &dsi->dev; \
    + ssize_t ret; \
    + ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d)); \
    + if (ret < 0) { \
    + dev_err_ratelimited(dev, "transmit data failed: %zd\n", \
    + ret); \
    + return ret; \
    + } \
    } while (0)

    /**
    --
    2.45.0.rc0.197.gbae5840b3b-goog

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