From: Marijn Suijten <marijn.suijten@somainline.org>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: phone-devel@vger.kernel.org, Andy Gross <agross@kernel.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Rob Herring <robh+dt@kernel.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>,
Bryan Wu <cooloney@gmail.com>,
linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org,
Courtney Cavin <courtney.cavin@sonymobile.com>
Subject: Re: [RESEND PATCH v2 04/13] backlight: qcom-wled: Fix off-by-one maximum with default num_strings
Date: Fri, 12 Nov 2021 13:35:01 +0100 [thread overview]
Message-ID: <20211112123501.pz5e6g7gavlinung@SoMainline.org> (raw)
In-Reply-To: <20211112120839.i6g747vewg6bkyk7@maple.lan>
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.
next prev parent reply other threads:[~2021-11-12 12:35 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-12 0:26 [RESEND PATCH v2 00/13] backlight: qcom-wled: fix and solidify handling of enabled-strings Marijn Suijten
2021-11-12 0:26 ` [RESEND PATCH v2 01/13] backlight: qcom-wled: Validate enabled string indices in DT Marijn Suijten
2021-11-12 11:54 ` Daniel Thompson
2021-11-12 0:26 ` [RESEND PATCH v2 02/13] backlight: qcom-wled: Pass number of elements to read to read_u32_array Marijn Suijten
2021-11-12 0:26 ` [RESEND PATCH v2 03/13] backlight: qcom-wled: Use cpu_to_le16 macro to perform conversion Marijn Suijten
2021-11-12 0:26 ` [RESEND PATCH v2 04/13] backlight: qcom-wled: Fix off-by-one maximum with default num_strings Marijn Suijten
2021-11-12 12:08 ` Daniel Thompson
2021-11-12 12:35 ` Marijn Suijten [this message]
2021-11-12 13:19 ` Daniel Thompson
2021-11-12 21:43 ` Marijn Suijten
2021-11-15 11:23 ` Daniel Thompson
2021-11-15 19:46 ` Marijn Suijten
2021-11-12 0:26 ` [RESEND PATCH v2 05/13] backlight: qcom-wled: Override default length with qcom,enabled-strings Marijn Suijten
2021-11-12 12:12 ` Daniel Thompson
2021-11-12 12:45 ` Marijn Suijten
2021-11-12 13:23 ` Daniel Thompson
2021-11-12 14:19 ` Marijn Suijten
2021-11-12 15:10 ` Daniel Thompson
2021-11-12 0:26 ` [RESEND PATCH v2 06/13] backlight: qcom-wled: Remove unnecessary 4th default string in WLED3 Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 07/13] backlight: qcom-wled: Provide enabled_strings default for WLED 4 and 5 Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 08/13] backlight: qcom-wled: Remove unnecessary double whitespace Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 09/13] backlight: qcom-wled: Respect enabled-strings in set_brightness Marijn Suijten
2021-11-12 12:20 ` Daniel Thompson
2021-11-12 0:27 ` [RESEND PATCH v2 10/13] arm64: dts: qcom: pmi8994: Fix "eternal"->"external" typo in WLED node Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 11/13] arm64: dts: qcom: pmi8994: Remove hardcoded linear WLED enabled-strings Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 12/13] arm64: dts: qcom: Move WLED num-strings from pmi8994 to sony-xperia-tone Marijn Suijten
2021-11-12 0:27 ` [RESEND PATCH v2 13/13] arm64: dt: qcom: pm660l: Remove board-specific WLED configuration Marijn Suijten
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