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[80.7.220.175]) by smtp.gmail.com with ESMTPSA id b6sm1207085wmb.1.2021.10.05.02.19.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Oct 2021 02:19:49 -0700 (PDT) Date: Tue, 5 Oct 2021 10:19:47 +0100 From: Daniel Thompson To: Marijn Suijten Cc: phone-devel@vger.kernel.org, Andy Gross , Bjorn Andersson , Lee Jones , Jingoo Han , ~postmarketos/upstreaming@lists.sr.ht, AngeloGioacchino Del Regno , Konrad Dybcio , Martin Botka , Jami Kettunen , Pavel Dubrova , Kiran Gunda , Courtney Cavin , Bryan Wu , 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 Message-ID: <20211005091947.7msztp5l554c7cy4@maple.lan> References: <20211004192741.621870-1-marijn.suijten@somainline.org> <20211004192741.621870-6-marijn.suijten@somainline.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211004192741.621870-6-marijn.suijten@somainline.org> Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org 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 > Reviewed-by: AngeloGioacchino Del Regno > --- > 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. > }; > > static const struct wled_var_cfg wled4_num_strings_cfg = { > .fn = wled3_num_strings_values_fn, > - .size = 4, > + .size = 5, /* [0, 4] */ Ditto. > }; > > static u32 wled3_switch_freq_values_fn(u32 idx) > @@ -1520,8 +1520,6 @@ 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)); > -- > 2.33.0 >