auxdisplay: ht16k33: don't access uninitialized data

arndb · gregkh · commit e1f990c24d14 · 2017-04-08T17:48:19.000+02:00
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 *)&amp;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 &lt;arnd@arndb.de&gt;
Reviewed-by: Robin van der Gracht &lt;robin@protonic.nl&gt;
Reviewed-by: Dmitry Torokhov &lt;dmitry.torokhov@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -278,7 +278,7 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)`
`278`	`278`	`}`
`279`	`279`	`}`
`280`	`280`	`input_sync(keypad->dev);`
`281`		`- memcpy(keypad->last_key_state, new_state, sizeof(new_state));`
	`281`	`+ memcpy(keypad->last_key_state, new_state, sizeof(u16) * keypad->cols);`
`282`	`282`
`283`	`283`	`return pressed;`
`284`	`284`	`}`
`@@ -353,6 +353,12 @@ static int ht16k33_keypad_probe(struct i2c_client *client,`
`353`	`353`	`err = matrix_keypad_parse_of_params(&client->dev, &rows, &cols);`
`354`	`354`	`if (err)`
`355`	`355`	`return err;`
	`356`	`+ if (rows > HT16K33_MATRIX_KEYPAD_MAX_ROWS \|\|`
	`357`	`+ cols > HT16K33_MATRIX_KEYPAD_MAX_COLS) {`
	`358`	`+ dev_err(&client->dev, "%u rows or %u cols out of range in DT\n",`
	`359`	`+ rows, cols);`
	`360`	`+ return -ERANGE;`
	`361`	`+ }`
`356`	`362`
`357`	`363`	`keypad->rows = rows;`
`358`	`364`	`keypad->cols = cols;`