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backlight: qcom-wled: Fix off-by-one maximum with default num_strings

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[ Upstream commit 5ada78b26f935f8751852dffa24f6b545b1d2517 ]

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>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211115203459.1634079-5-marijn.suijten@somainline.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Marijn Suijten 2021-11-15 21:34:54 +01:00 committed by Greg Kroah-Hartman
parent 09aed85e8c
commit bf4daf6153
1 changed files with 16 additions and 32 deletions
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48
drivers/video/backlight/qcom-wled.c
View File

@ -1256,21 +1256,6 @@ 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));
@ -1344,11 +1329,6 @@ 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[] = {
@ -1372,11 +1352,6 @@ 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[] = {
@ -1400,11 +1375,6 @@ 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,
@ -1523,8 +1493,6 @@ 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));
@ -1555,6 +1523,22 @@ 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;
}