[PATCH v3 1/1] gpiolib: acpi: Fix potential out-of-boundary left shift

[PATCH v3 1/1] gpiolib: acpi: Fix potential out-of-boundary left shift

[Andy Shevchenko]

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.

Fixes: 59084c564c41 ("gpiolib: acpi: use BIT_ULL() for u64 mask in address space handler")
Fixes: 2c4d00cb8fc5 ("gpiolib: acpi: Use BIT() macro to increase readability")
Cc: stable@vger.kernel.org
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
v3: added requested and given tags (Bart, Mika)
 drivers/gpio/gpiolib-acpi-core.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib-acpi-core.c b/drivers/gpio/gpiolib-acpi-core.c
index d42f769eeb11..9627b3a9c7f3 100644
--- a/drivers/gpio/gpiolib-acpi-core.c
+++ b/drivers/gpio/gpiolib-acpi-core.c
@@ -1104,6 +1104,7 @@ acpi_gpio_adr_space_handler(u32 function, acpi_physical_address address,
 		unsigned int pin = agpio->pin_table[i];
 		struct acpi_gpio_connection *conn;
 		struct gpio_desc *desc;
+		u16 word, shift;
 		bool found;
 
 		mutex_lock(&achip->conn_lock);
@@ -1158,10 +1159,22 @@ acpi_gpio_adr_space_handler(u32 function, acpi_physical_address address,
 
 		mutex_unlock(&achip->conn_lock);
 
-		if (function == ACPI_WRITE)
-			gpiod_set_raw_value_cansleep(desc, !!(*value & BIT_ULL(i)));
-		else
-			*value |= (u64)gpiod_get_raw_value_cansleep(desc) << i;
+		/*
+		 * For the cases when OperationRegion() consists of more than
+		 * 64 bits calculate the word and bit shift to use that one to
+		 * access the value.
+		 */
+		word = i / 64;
+		shift = i % 64;
+
+		if (function == ACPI_WRITE) {
+			gpiod_set_raw_value_cansleep(desc, value[word] & BIT_ULL(shift));
+		} else {
+			if (gpiod_get_raw_value_cansleep(desc))
+				value[word] |= BIT_ULL(shift);
+			else
+				value[word] &= ~BIT_ULL(shift);
+		}
 	}
 
 out:
-- 
2.50.1

Re: [PATCH v3 1/1] gpiolib: acpi: Fix potential out-of-boundary left shift

[Bartosz Golaszewski]

On Wed, 28 Jan 2026 10:58:54 +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.
> 
> [...]

Applied, thanks!

[1/1] gpiolib: acpi: Fix potential out-of-boundary left shift
      https://git.kernel.org/brgl/c/e64d1cb21a1c6ecd51bc1c94c83f6fc656f7c94d

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>