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From: Guenter Roeck <linux@roeck-us.net>
To: Rosen Penev <rosenp@gmail.com>
Cc: "Pali Rohár" <pali@kernel.org>, "Arnd Bergmann" <arnd@arndb.de>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] hwmon: (dell-smm) Reject a fan_max that the BIOS cannot take
Date: Sat, 14 Nov 2026 08:52:53 -0800	[thread overview]
Message-ID: <73e9e9be-96fc-4189-8d86-7c4059b7f676@roeck-us.net> (raw)
In-Reply-To: <6d3b86acf6713e9286e60ecf788582e840946238.1794633179.git.rosenp@gmail.com>

On Fri, Nov 13, 2026 at 10:20:23PM -0800, Rosen Penev wrote:
> The fan_max module parameter is used without any range check, unlike
> fan_mult. dell_smm_init_hwmon() allocates the nominal speed table with
> 
> 	devm_kmalloc_array(dev, data->i8k_fan_max + 1, ...)
> 
> and fan_max=4294967295 wraps the count to 0. devm_kmalloc() then
> returns ZERO_SIZE_PTR, which the first successful nominal speed call
> writes through.
> 
> Values above 255 are also meaningless: the fan state is passed to the
> BIOS as fan | (speed << 8), so the higher bits end up in other parts of
> the request. Large values that do not wrap still cost one SMM call per
> state and fan while probing.
> 
> Fail probing if the maximum fan state does not fit in a byte, like the
> existing check for fan_mult.
> 
> Fixes: 81474fc2fae9 ("i8k: Add support for configurable maximum fan speed value")
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

Applied.

Thanks,
Guenter

  reply	other threads:[~2026-11-14 16:52 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-14  6:20 [PATCH 0/2] hwmon: (dell-smm) Validate pwm and fan_max values Rosen Penev
2026-11-14  6:20 ` [PATCH 1/2] hwmon: (dell-smm) Clamp the pwm value before scaling it Rosen Penev
2026-11-14 16:51   ` Guenter Roeck
2026-11-14  6:20 ` [PATCH 2/2] hwmon: (dell-smm) Reject a fan_max that the BIOS cannot take Rosen Penev
2026-11-14 16:52   ` Guenter Roeck [this message]
2026-11-14  6:29 ` [PATCH 0/3] platform/x86: dell-laptop: Fix keyboard backlight and charge threshold handling Rosen Penev
2026-11-14  6:29 ` [PATCH 1/3] platform/x86: dell-laptop: Reject keyboard backlight timeouts that overflow Rosen Penev
2026-11-14  6:29 ` [PATCH 2/3] platform/x86: dell-laptop: Don't use an unread keyboard state at init Rosen Penev
2026-11-14  6:29 ` [PATCH 3/3] platform/x86: dell-laptop: Parse the charge end threshold as an int Rosen Penev

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