[PATCH] auxdisplay: ht16k33: don't access uninitialized data

[PATCH] auxdisplay: ht16k33: don't access uninitialized data

[Arnd Bergmann]

gcc-7.0.1 points out that we copy uninitialized data from the stack
into a per-device structure:

drivers/auxdisplay/ht16k33.c: In function 'ht16k33_keypad_irq_thread':
arch/x86/include/asm/string_32.h:78:16: error: 'new_state' may be used uninitialized in this function [-Werror=maybe-uninitialized]
arch/x86/include/asm/string_32.h:79:22: error: '*((void *)&new_state+4)' may be used uninitialized in this function [-Werror=maybe-uninitialized]

The access is harmless because we never read the data, but we are better
off not doing this, so this changes the code to only copy the data
that was actually initialized. To make sure we don't overflow the
stack with an incorrect DT, we also need to add a sanity checkin the
probe function.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/auxdisplay/ht16k33.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index f66b45b235b0..ba6370974574 100644
--- a/drivers/auxdisplay/ht16k33.c
+++ b/drivers/auxdisplay/ht16k33.c
@@ -278,7 +278,7 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
 		}
 	}
 	input_sync(keypad->dev);
-	memcpy(keypad->last_key_state, new_state, sizeof(new_state));
+	memcpy(keypad->last_key_state, new_state, sizeof(u16) * keypad->cols);
 
 	return pressed;
 }
@@ -353,6 +353,12 @@ static int ht16k33_keypad_probe(struct i2c_client *client,
 	err = matrix_keypad_parse_of_params(&client->dev, &rows, &cols);
 	if (err)
 		return err;
+	if (rows > HT16K33_MATRIX_KEYPAD_MAX_ROWS ||
+	    cols > HT16K33_MATRIX_KEYPAD_MAX_COLS) {
+		dev_err(&client->dev, "%u rows or %u cols out of range in DT\n",
+			rows, cols);
+		return -ERANGE;
+	}
 
 	keypad->rows = rows;
 	keypad->cols = cols;
-- 
2.9.0

Re: [PATCH] auxdisplay: ht16k33: don't access uninitialized data

[Dmitry Torokhov]

On Tue, Mar 28, 2017 at 12:11:49PM +0200, Arnd Bergmann wrote:
> gcc-7.0.1 points out that we copy uninitialized data from the stack
> into a per-device structure:
> 
> drivers/auxdisplay/ht16k33.c: In function 'ht16k33_keypad_irq_thread':
> arch/x86/include/asm/string_32.h:78:16: error: 'new_state' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/include/asm/string_32.h:79:22: error: '*((void *)&new_state+4)' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> The access is harmless because we never read the data, but we are better
> off not doing this, so this changes the code to only copy the data
> that was actually initialized. To make sure we don't overflow the
> stack with an incorrect DT, we also need to add a sanity checkin the
> probe function.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

> ---
>  drivers/auxdisplay/ht16k33.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
> index f66b45b235b0..ba6370974574 100644
> --- a/drivers/auxdisplay/ht16k33.c
> +++ b/drivers/auxdisplay/ht16k33.c
> @@ -278,7 +278,7 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
>  		}
>  	}
>  	input_sync(keypad->dev);
> -	memcpy(keypad->last_key_state, new_state, sizeof(new_state));
> +	memcpy(keypad->last_key_state, new_state, sizeof(u16) * keypad->cols);
>  
>  	return pressed;
>  }
> @@ -353,6 +353,12 @@ static int ht16k33_keypad_probe(struct i2c_client *client,
>  	err = matrix_keypad_parse_of_params(&client->dev, &rows, &cols);
>  	if (err)
>  		return err;
> +	if (rows > HT16K33_MATRIX_KEYPAD_MAX_ROWS ||
> +	    cols > HT16K33_MATRIX_KEYPAD_MAX_COLS) {
> +		dev_err(&client->dev, "%u rows or %u cols out of range in DT\n",
> +			rows, cols);
> +		return -ERANGE;
> +	}
>  
>  	keypad->rows = rows;
>  	keypad->cols = cols;
> -- 
> 2.9.0
> 

-- 
Dmitry

Re: [PATCH] auxdisplay: ht16k33: don't access uninitialized data

[Robin van der Gracht]

On Tue, 28 Mar 2017 12:11:49 +0200
Arnd Bergmann <arnd@arndb.de> wrote:

> gcc-7.0.1 points out that we copy uninitialized data from the stack
> into a per-device structure:
> 
> drivers/auxdisplay/ht16k33.c: In function 'ht16k33_keypad_irq_thread':
> arch/x86/include/asm/string_32.h:78:16: error: 'new_state' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/include/asm/string_32.h:79:22: error: '*((void *)&new_state+4)' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> The access is harmless because we never read the data, but we are better
> off not doing this, so this changes the code to only copy the data
> that was actually initialized. To make sure we don't overflow the
> stack with an incorrect DT, we also need to add a sanity checkin the
> probe function.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Robin van der Gracht <robin@protonic.nl>

> ---
>  drivers/auxdisplay/ht16k33.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
> index f66b45b235b0..ba6370974574 100644
> --- a/drivers/auxdisplay/ht16k33.c
> +++ b/drivers/auxdisplay/ht16k33.c
> @@ -278,7 +278,7 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
>  		}
>  	}
>  	input_sync(keypad->dev);
> -	memcpy(keypad->last_key_state, new_state, sizeof(new_state));
> +	memcpy(keypad->last_key_state, new_state, sizeof(u16) * keypad->cols);
>  
>  	return pressed;
>  }
> @@ -353,6 +353,12 @@ static int ht16k33_keypad_probe(struct i2c_client *client,
>  	err = matrix_keypad_parse_of_params(&client->dev, &rows, &cols);
>  	if (err)
>  		return err;
> +	if (rows > HT16K33_MATRIX_KEYPAD_MAX_ROWS ||
> +	    cols > HT16K33_MATRIX_KEYPAD_MAX_COLS) {
> +		dev_err(&client->dev, "%u rows or %u cols out of range in DT\n",
> +			rows, cols);
> +		return -ERANGE;
> +	}
>  
>  	keypad->rows = rows;
>  	keypad->cols = cols;