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drm/mipi-dsi: Fix theoretical int overflow in mipi_dsi_dcs_write_seq()

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The mipi_dsi_dcs_write_seq() macro makes a call to
mipi_dsi_dcs_write_buffer() 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_dcs_write_seq(dsi, cmd, <32767 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: 2a9e9daf75 ("drm/mipi-dsi: Introduce mipi_dsi_dcs_write_seq macro")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240514102056.v5.1.I30fa4c8348ea316c886ef8a522a52fed617f930d@changeid
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514102056.v5.1.I30fa4c8348ea316c886ef8a522a52fed617f930d@changeid
This commit is contained in:
Douglas Anderson
2024-05-14 10:20:51 -07:00
committed by Neil Armstrong
parent 216afc2c11
commit 0b03829fde
1 changed files with 12 additions and 12 deletions
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24
include/drm/drm_mipi_dsi.h
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@@ -333,18 +333,18 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
* @cmd: Command
* @seq: buffer containing data to be transmitted
*/
#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
do { \
static const u8 d[] = { cmd, seq }; \
struct device *dev = &dsi->dev; \
int ret; \
ret = mipi_dsi_dcs_write_buffer(dsi, d, ARRAY_SIZE(d)); \
if (ret < 0) { \
dev_err_ratelimited( \
dev, "sending command %#02x failed: %d\n", \
cmd, ret); \
return ret; \
} \
#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
do { \
static const u8 d[] = { cmd, seq }; \
struct device *dev = &dsi->dev; \
ssize_t ret; \
ret = mipi_dsi_dcs_write_buffer(dsi, d, ARRAY_SIZE(d)); \
if (ret < 0) { \
dev_err_ratelimited( \
dev, "sending command %#02x failed: %zd\n", \
cmd, ret); \
return ret; \
} \
} while (0)
/**