| Message ID | 20211112002706.453289-5-marijn.suijten@somainline.org |
|---|---|
| State | New |
| Headers | show |
| Series | backlight: qcom-wled: fix and solidify handling of enabled-strings | expand |
On 2021-11-12 12:08:39, Daniel Thompson wrote: > On Fri, Nov 12, 2021 at 01:26:57AM +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 allows more stringent checks on the maximum value when > > qcom,enabled-strings is provided in the DT. Note that num-strings is > > parsed after enabled-strings to give it final sign-off over the length, > > which DT currently utilizes to get around an incorrect fixed read of > > four elements from that array (has been addressed in a prior patch). > > > > 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 | 51 +++++++++++------------------ > > 1 file changed, 19 insertions(+), 32 deletions(-) > > > > diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c > > index 977cd75827d7..c5232478a343 100644 > > --- a/drivers/video/backlight/qcom-wled.c > > +++ b/drivers/video/backlight/qcom-wled.c > > @@ -1552,6 +1520,25 @@ 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) { > > + dev_warn(dev, "qcom,num-strings and qcom,enabled-strings are ambiguous\n"); > > The warning should also be below the error message on the next if statement. Agreed. > This warning occurs even when there is no ambiguity. > > This could be: > > if (string_len > 0 && val != string_len) > > Combined these changes allows us to give a much more helpful and assertive > warning message: > > qcom,num-strings mis-matches and will partially override > qcom,enabled-strings (remove qcom,num-strings?) I want to let the user know it's set regardless of whether they're equivalent; no need to set both. How about: Only one of qcom,num-strings or qcom,enabled-strings should be set That should be more descriptive? Otherwise, let me know if you really want to allow users to (unnecessarily) set both - or if it can / should be caught in DT validation instead. - Marijn > > + if (val > string_len) { > > + dev_err(dev, "qcom,num-strings exceeds qcom,enabled-strings\n"); > > + return -EINVAL; > > + } > > + } > > > Daniel.
On Fri, Nov 12, 2021 at 01:35:01PM +0100, Marijn Suijten wrote: > On 2021-11-12 12:08:39, Daniel Thompson wrote: > > On Fri, Nov 12, 2021 at 01:26:57AM +0100, Marijn Suijten wrote: > > > + if (string_len > 0) { > > > + dev_warn(dev, "qcom,num-strings and qcom,enabled-strings are ambiguous\n"); > > > > The warning should also be below the error message on the next if statement. > > Agreed. > > > This warning occurs even when there is no ambiguity. > > > > This could be: > > > > if (string_len > 0 && val != string_len) > > > > Combined these changes allows us to give a much more helpful and assertive > > warning message: > > > > qcom,num-strings mis-matches and will partially override > > qcom,enabled-strings (remove qcom,num-strings?) > > I want to let the user know it's set regardless of whether they're > equivalent; no need to set both. > > How about: > > Only one of qcom,num-strings or qcom,enabled-strings should be set > > That should be more descriptive? Otherwise, let me know if you really > want to allow users to (unnecessarily) set both - or if it can / should > be caught in DT validation instead. Yes. I can live with that text. Let's use that. Maybe I wouldn't if there gazilions of existing DTs with both properties but IIRC the number is likely to be small or zero (although we couldn't be 100% sure which). Daniel.
diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c index 977cd75827d7..c5232478a343 100644 --- a/drivers/video/backlight/qcom-wled.c +++ b/drivers/video/backlight/qcom-wled.c @@ -1253,21 +1253,6 @@ 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)); @@ -1341,11 +1326,6 @@ 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[] = { @@ -1369,11 +1349,6 @@ 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[] = { @@ -1397,11 +1372,6 @@ 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, @@ -1520,8 +1490,6 @@ 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)); @@ -1552,6 +1520,25 @@ 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) { + dev_warn(dev, "qcom,num-strings and qcom,enabled-strings are ambiguous\n"); + if (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 allows more stringent checks on the maximum value when qcom,enabled-strings is provided in the DT. Note that num-strings is parsed after enabled-strings to give it final sign-off over the length, which DT currently utilizes to get around an incorrect fixed read of four elements from that array (has been addressed in a prior patch). 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 | 51 +++++++++++------------------ 1 file changed, 19 insertions(+), 32 deletions(-) -- 2.33.0