| Message ID | 20211115203459.1634079-5-marijn.suijten@somainline.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | backlight: qcom-wled: fix and solidify handling of enabled-strings | expand |
On Mon, Nov 15, 2021 at 09:34:54PM +0100, Marijn Suijten wrote: > When not specifying num-strings in the DT the default is used, but +1 is > added to it which turns WLED3 into 4 and WLED4/5 into 5 strings instead > of 3 and 4 respectively, causing out-of-bounds reads and register > read/writes. This +1 exists for a deficiency in the DT parsing code, > and is simply omitted entirely - solving this oob issue - by parsing the > property separately much like qcom,enabled-strings. > > This also enables more stringent checks on the maximum value when > qcom,enabled-strings is provided in the DT, by parsing num-strings after > enabled-strings to allow it to check against (and in a subsequent patch > override) the length of enabled-strings: it is invalid to set > num-strings higher than that. > The DT currently utilizes it to get around an incorrect fixed read of > four elements from that array (has been addressed in a prior patch) by > setting a lower num-strings where desired. > > Fixes: 93c64f1ea1e8 ("leds: add Qualcomm PM8941 WLED driver") > Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org> > Reviewed-By: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Daniel.
On Mon, 15 Nov 2021, Marijn Suijten wrote: > When not specifying num-strings in the DT the default is used, but +1 is > added to it which turns WLED3 into 4 and WLED4/5 into 5 strings instead > of 3 and 4 respectively, causing out-of-bounds reads and register > read/writes. This +1 exists for a deficiency in the DT parsing code, > and is simply omitted entirely - solving this oob issue - by parsing the > property separately much like qcom,enabled-strings. > > This also enables more stringent checks on the maximum value when > qcom,enabled-strings is provided in the DT, by parsing num-strings after > enabled-strings to allow it to check against (and in a subsequent patch > override) the length of enabled-strings: it is invalid to set > num-strings higher than that. > The DT currently utilizes it to get around an incorrect fixed read of > four elements from that array (has been addressed in a prior patch) by > setting a lower num-strings where desired. > > Fixes: 93c64f1ea1e8 ("leds: add Qualcomm PM8941 WLED driver") > Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org> > Reviewed-By: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org> > --- > drivers/video/backlight/qcom-wled.c | 48 ++++++++++------------------- > 1 file changed, 16 insertions(+), 32 deletions(-) Applied, thanks.
diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c index 9d883e702134..ab10910971e9 100644 --- a/drivers/video/backlight/qcom-wled.c +++ b/drivers/video/backlight/qcom-wled.c @@ -1255,21 +1255,6 @@ static const struct wled_var_cfg wled5_ovp_cfg = { .size = 16, }; -static u32 wled3_num_strings_values_fn(u32 idx) -{ - return idx + 1; -} - -static const struct wled_var_cfg wled3_num_strings_cfg = { - .fn = wled3_num_strings_values_fn, - .size = 3, -}; - -static const struct wled_var_cfg wled4_num_strings_cfg = { - .fn = wled3_num_strings_values_fn, - .size = 4, -}; - static u32 wled3_switch_freq_values_fn(u32 idx) { return 19200 / (2 * (1 + idx)); @@ -1343,11 +1328,6 @@ static int wled_configure(struct wled *wled) .val_ptr = &cfg->switch_freq, .cfg = &wled3_switch_freq_cfg, }, - { - .name = "qcom,num-strings", - .val_ptr = &cfg->num_strings, - .cfg = &wled3_num_strings_cfg, - }, }; const struct wled_u32_opts wled4_opts[] = { @@ -1371,11 +1351,6 @@ static int wled_configure(struct wled *wled) .val_ptr = &cfg->switch_freq, .cfg = &wled3_switch_freq_cfg, }, - { - .name = "qcom,num-strings", - .val_ptr = &cfg->num_strings, - .cfg = &wled4_num_strings_cfg, - }, }; const struct wled_u32_opts wled5_opts[] = { @@ -1399,11 +1374,6 @@ static int wled_configure(struct wled *wled) .val_ptr = &cfg->switch_freq, .cfg = &wled3_switch_freq_cfg, }, - { - .name = "qcom,num-strings", - .val_ptr = &cfg->num_strings, - .cfg = &wled4_num_strings_cfg, - }, { .name = "qcom,modulator-sel", .val_ptr = &cfg->mod_sel, @@ -1522,8 +1492,6 @@ static int wled_configure(struct wled *wled) *bool_opts[i].val_ptr = true; } - cfg->num_strings = cfg->num_strings + 1; - string_len = of_property_count_elems_of_size(dev->of_node, "qcom,enabled-strings", sizeof(u32)); @@ -1554,6 +1522,22 @@ static int wled_configure(struct wled *wled) } } + rc = of_property_read_u32(dev->of_node, "qcom,num-strings", &val); + if (!rc) { + if (val < 1 || val > wled->max_string_count) { + dev_err(dev, "qcom,num-strings must be between 1 and %d\n", + wled->max_string_count); + return -EINVAL; + } + + if (string_len > 0 && val > string_len) { + dev_err(dev, "qcom,num-strings exceeds qcom,enabled-strings\n"); + return -EINVAL; + } + + cfg->num_strings = val; + } + return 0; }
When not specifying num-strings in the DT the default is used, but +1 is added to it which turns WLED3 into 4 and WLED4/5 into 5 strings instead of 3 and 4 respectively, causing out-of-bounds reads and register read/writes. This +1 exists for a deficiency in the DT parsing code, and is simply omitted entirely - solving this oob issue - by parsing the property separately much like qcom,enabled-strings. This also enables more stringent checks on the maximum value when qcom,enabled-strings is provided in the DT, by parsing num-strings after enabled-strings to allow it to check against (and in a subsequent patch override) the length of enabled-strings: it is invalid to set num-strings higher than that. The DT currently utilizes it to get around an incorrect fixed read of four elements from that array (has been addressed in a prior patch) by setting a lower num-strings where desired. Fixes: 93c64f1ea1e8 ("leds: add Qualcomm PM8941 WLED driver") Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org> Reviewed-By: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org> --- drivers/video/backlight/qcom-wled.c | 48 ++++++++++------------------- 1 file changed, 16 insertions(+), 32 deletions(-)