From: Colin Ian King <colin.king@canonical.com>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>,
Jingoo Han <jingoohan1@gmail.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Gyungoh Yoo <jack.yoo@skyworksinc.com>,
Bryan Wu <cooloney@gmail.com>,
dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][V2] backlight: sky81452: insure while loop does not allow negative array indexing
Date: Thu, 27 Feb 2020 15:10:43 +0000 [thread overview]
Message-ID: <b0e21719-3a7c-099a-292d-c3fa65a84fe8@canonical.com> (raw)
In-Reply-To: <20200227114623.vaevrdwiduxa2mqs@holly.lan>
On 27/02/2020 11:46, Daniel Thompson wrote:
> On Wed, Feb 26, 2020 at 07:58:26PM +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> In the unlikely event that num_entry is zero, the while loop
>> pre-decrements num_entry to cause negative array indexing into the
>> array sources. Fix this by iterating only if num_entry >= 0.
>>
>> Addresses-Coverity: ("Out-of-bounds read")
>> Fixes: f705806c9f35 ("backlight: Add support Skyworks SKY81452 backlight driver")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>
>> V2: fix typo in commit subject line
>
> Isn't the correct spelling "ensure"?
It is. V1 is correct after all. Doh.
>
>
>> ---
>> drivers/video/backlight/sky81452-backlight.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/backlight/sky81452-backlight.c b/drivers/video/backlight/sky81452-backlight.c
>> index 2355f00f5773..f456930ce78e 100644
>> --- a/drivers/video/backlight/sky81452-backlight.c
>> +++ b/drivers/video/backlight/sky81452-backlight.c
>> @@ -200,7 +200,7 @@ static struct sky81452_bl_platform_data *sky81452_bl_parse_dt(
>> }
>>
>> pdata->enable = 0;
>> - while (--num_entry)
>> + while (--num_entry >= 0)
>> pdata->enable |= (1 << sources[num_entry]);
>
> This look still looks buggy to me (so I'd second Walter's request to
> change it to a for loop). If the code genuinely does not contain a
> bug then it probably needs a prominent comment explaining why it is
> correct not to honour sources[0]!
>
>
> Daniel.
>
next prev parent reply other threads:[~2020-02-27 15:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 19:58 [PATCH][V2] backlight: sky81452: insure while loop does not allow negative array indexing Colin King
2020-02-27 11:15 ` AW: " Walter Harms
2020-02-27 11:46 ` Daniel Thompson
2020-02-27 14:57 ` Daniel Thompson
2020-02-27 15:10 ` Colin Ian King [this message]
2020-02-28 16:45 ` Daniel Thompson
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