linux-kernel - Re: [PATCH v2 1/1] gpiolib: acpi: Fix potential out-of-boundary left shift

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Message-ID: <20260127134300.GK2275908@black.igk.intel.com>
Date: Tue, 27 Jan 2026 14:43:00 +0100
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Mika Westerberg <westeri@...nel.org>, linux-gpio@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Walleij <linusw@...nel.org>,
	Bartosz Golaszewski <brgl@...nel.org>
Subject: Re: [PATCH v2 1/1] gpiolib: acpi: Fix potential out-of-boundary left
 shift

On Tue, Jan 27, 2026 at 12:06:30PM +0100, Andy Shevchenko wrote:
> GPIO Address Space handler gets a pointer to the in or out value.
> This value is supposed to be at least 64-bit, but it's not limited
> to be exactly 64-bit. When ACPI tables are being parsed, for
> the bigger Connection():s ACPICA creates a Buffer instead of regular
> Integer object. The Buffer exists as long as Namespace holds
> the certain Connection(). Hence we can access the necessary bits
> without worrying. On the other hand, the left shift, used in
> the code, is limited by 31 (on 32-bit platforms) and otherwise
> considered to be Undefined Behaviour. Also the code uses only
> the first 64-bit word for the value, and anything bigger than 63
> will be also subject to UB. Fix all this by modifying the code
> to correctly set or clear the respective bit in the bitmap constructed
> of 64-bit words.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Perfect, thanks!

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>