[PATCH v3 4/9] backlight: qcom-wled: Fix off-by-one maximum with default num_strings
From: Marijn Suijten <marijn.suijten@somainline.org>
Date: 2021-11-16 00:07:31
Also in:
dri-devel, linux-arm-msm, linux-devicetree, lkml, phone-devel
Subsystem:
arm/qualcomm mailing list, backlight class/subsystem, framebuffer layer, the rest · Maintainers:
Lee Jones, Daniel Thompson, Jingoo Han, Helge Deller, Linus Torvalds
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 <redacted>
---
drivers/video/backlight/qcom-wled.c | 48 ++++++++++-------------------
1 file changed, 16 insertions(+), 32 deletions(-)
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; }
--
2.33.1