From: Daniel Thompson <daniel.thompson@linaro.org>
To: Marijn Suijten <marijn.suijten@somainline.org>
Cc: phone-devel@vger.kernel.org, Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Lee Jones <lee.jones@linaro.org>,
Jingoo Han <jingoohan1@gmail.com>,
~postmarketos/upstreaming@lists.sr.ht,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@somainline.org>,
Konrad Dybcio <konrad.dybcio@somainline.org>,
Martin Botka <martin.botka@somainline.org>,
Jami Kettunen <jami.kettunen@somainline.org>,
Pavel Dubrova <pashadubrova@gmail.com>,
Kiran Gunda <kgunda@codeaurora.org>,
Courtney Cavin <courtney.cavin@sonymobile.com>,
Bryan Wu <cooloney@gmail.com>,
linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/10] backlight: qcom-wled: Fix off-by-one maximum with default num_strings
Date: Tue, 5 Oct 2021 11:53:12 +0100 [thread overview]
Message-ID: <20211005105312.kqiyzoqtzzjxayhg@maple.lan> (raw)
In-Reply-To: <20211005103843.heufyonycnudxnzd@maple.lan>
On Tue, Oct 05, 2021 at 11:38:43AM +0100, Daniel Thompson wrote:
> On Tue, Oct 05, 2021 at 12:06:06PM +0200, Marijn Suijten wrote:
> > On 2021-10-05 10:19:47, Daniel Thompson wrote:
> > > On Mon, Oct 04, 2021 at 09:27:36PM +0200, 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 allowing
> > > > one extra iteration of the wled_var_cfg function parsing this particular
> > > > property.
> > > >
> > > > 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 | 8 +++-----
> > > > 1 file changed, 3 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> > > > index 27e8949c7922..66ce77ee3099 100644
> > > > --- a/drivers/video/backlight/qcom-wled.c
> > > > +++ b/drivers/video/backlight/qcom-wled.c
> > > > @@ -1255,17 +1255,17 @@ static const struct wled_var_cfg wled5_ovp_cfg = {
> > > >
> > > > static u32 wled3_num_strings_values_fn(u32 idx)
> > > > {
> > > > - return idx + 1;
> > > > + return idx;
>
>
> > > > }
> > > >
> > > > static const struct wled_var_cfg wled3_num_strings_cfg = {
> > > > .fn = wled3_num_strings_values_fn,
> > > > - .size = 3,
> > > > + .size = 4, /* [0, 3] */
> > >
> > > 0 is not a valid value for this property.
> >
> > These comments represent the possible loop iterations the DT "cfg
> > parser" runs through, starting at j=0 and running up until and including
> > j=3. Should I make that more clear or omit these comments entirely?
>
> The role of wled3_num_strings_values_fn() is to enumerate the list of
> legal values for the property [ 1, 2, 3 ]. Your changes cause the
> enumeration to include a non-legal value so that you can have an
> identity mapping between the symbol and the enumerate value.
>
> An alternative approach would be to leave the enumeration logic
> alone but set the num_string default to UINT_MAX in all cases:
>
> - cfg->num_strings = cfg->num_strings + 1;
> + if (cfg->num_strings == UINT_MAX)
> + cfg->num_strings =
Oops... looks like I missed the cfg->max_string_count here.
> + else
> + /* Convert from enumerated to numeric form */
> + cfg->num_strings = wled3_num_strings_values_fn(
> + cfg->num_strings);
PS the alternative option is not to treat num-strings as an enumerated
value at all and just read it directly without using wled_values()...
next prev parent reply other threads:[~2021-10-05 10:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 19:27 [PATCH 00/10] backlight: qcom-wled: fix and solidify handling of enabled-strings Marijn Suijten
2021-10-04 19:27 ` [PATCH 01/10] backlight: qcom-wled: Pass number of elements to read to read_u32_array Marijn Suijten
2021-10-05 9:05 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 02/10] backlight: qcom-wled: Use cpu_to_le16 macro to perform conversion Marijn Suijten
2021-10-05 9:06 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 03/10] backlight: qcom-wled: Override num-strings when enabled-strings is set Marijn Suijten
2021-10-05 9:38 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 04/10] backlight: qcom-wled: Validate enabled string indices in DT Marijn Suijten
2021-10-05 9:14 ` Daniel Thompson
2021-10-05 10:03 ` Marijn Suijten
2021-10-05 10:42 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 05/10] backlight: qcom-wled: Fix off-by-one maximum with default num_strings Marijn Suijten
2021-10-05 9:19 ` Daniel Thompson
2021-10-05 10:06 ` Marijn Suijten
2021-10-05 10:38 ` Daniel Thompson
2021-10-05 10:53 ` Daniel Thompson [this message]
2021-10-05 11:44 ` Marijn Suijten
2021-10-05 14:03 ` Daniel Thompson
2021-10-05 15:23 ` Marijn Suijten
2021-10-05 16:24 ` Daniel Thompson
2021-10-05 16:50 ` Konrad Dybcio
2021-10-05 17:34 ` Marijn Suijten
2021-10-06 14:44 ` Daniel Thompson
2021-10-07 21:28 ` Marijn Suijten
2021-10-04 19:27 ` [PATCH 06/10] backlight: qcom-wled: Remove unnecessary 4th default string in wled3 Marijn Suijten
2021-10-05 9:20 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 07/10] backlight: qcom-wled: Provide enabled_strings default for wled 4 and 5 Marijn Suijten
2021-10-05 9:21 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 08/10] backlight: qcom-wled: Remove unnecessary double whitespace Marijn Suijten
2021-10-05 9:21 ` Daniel Thompson
2021-10-04 19:27 ` [PATCH 09/10] backlight: qcom-wled: Consistently use enabled-strings in set_brightness Marijn Suijten
2021-10-05 9:33 ` Daniel Thompson
2021-10-05 10:12 ` Marijn Suijten
2021-10-04 19:27 ` [PATCH 10/10] backlight: qcom-wled: Consider enabled_strings in autodetection Marijn Suijten
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