1 files changed, 89 insertions, 15 deletions

diff --git a/drivers/input/input.c b/drivers/input/input.c
index f71ea4fb17..3212c63dcf 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1378,19 +1378,19 @@ static int input_print_modalias_bits(char *buf, int size,
 				     char name, const unsigned long *bm,
 				     unsigned int min_bit, unsigned int max_bit)
 {
-	int len = 0, i;
+	int bit = min_bit;
+	int len = 0;
 
 	len += snprintf(buf, max(size, 0), "%c", name);
-	for (i = min_bit; i < max_bit; i++)
-		if (bm[BIT_WORD(i)] & BIT_MASK(i))
-			len += snprintf(buf + len, max(size - len, 0), "%X,", i);
+	for_each_set_bit_from(bit, bm, max_bit)
+		len += snprintf(buf + len, max(size - len, 0), "%X,", bit);
 	return len;
 }
 
-static int input_print_modalias(char *buf, int size, const struct input_dev *id,
-				int add_cr)
+static int input_print_modalias_parts(char *buf, int size, int full_len,
+				      const struct input_dev *id)
 {
-	int len;
+	int len, klen, remainder, space;
 
 	len = snprintf(buf, max(size, 0),
 		       "input:b%04Xv%04Xp%04Xe%04X-",
@@ -1399,8 +1399,48 @@ static int input_print_modalias(char *buf, int size, const struct input_dev *id,
 
 	len += input_print_modalias_bits(buf + len, size - len,
 				'e', id->evbit, 0, EV_MAX);
-	len += input_print_modalias_bits(buf + len, size - len,
+
+	/*
+	 * Calculate the remaining space in the buffer making sure we
+	 * have place for the terminating 0.
+	 */
+	space = max(size - (len + 1), 0);
+
+	klen = input_print_modalias_bits(buf + len, size - len,
 				'k', id->keybit, KEY_MIN_INTERESTING, KEY_MAX);
+	len += klen;
+
+	/*
+	 * If we have more data than we can fit in the buffer, check
+	 * if we can trim key data to fit in the rest. We will indicate
+	 * that key data is incomplete by adding "+" sign at the end, like
+	 * this: * "k1,2,3,45,+,".
+	 *
+	 * Note that we shortest key info (if present) is "k+," so we
+	 * can only try to trim if key data is longer than that.
+	 */
+	if (full_len && size < full_len + 1 && klen > 3) {
+		remainder = full_len - len;
+		/*
+		 * We can only trim if we have space for the remainder
+		 * and also for at least "k+," which is 3 more characters.
+		 */
+		if (remainder <= space - 3) {
+			/*
+			 * We are guaranteed to have 'k' in the buffer, so
+			 * we need at least 3 additional bytes for storing
+			 * "+," in addition to the remainder.
+			 */
+			for (int i = size - 1 - remainder - 3; i >= 0; i--) {
+				if (buf[i] == 'k' || buf[i] == ',') {
+					strcpy(buf + i + 1, "+,");
+					len = i + 3; /* Not counting '\0' */
+					break;
+				}
+			}
+		}
+	}
+
 	len += input_print_modalias_bits(buf + len, size - len,
 				'r', id->relbit, 0, REL_MAX);
 	len += input_print_modalias_bits(buf + len, size - len,
@@ -1416,12 +1456,25 @@ static int input_print_modalias(char *buf, int size, const struct input_dev *id,
 	len += input_print_modalias_bits(buf + len, size - len,
 				'w', id->swbit, 0, SW_MAX);
 
-	if (add_cr)
-		len += snprintf(buf + len, max(size - len, 0), "\n");
-
 	return len;
 }
 
+static int input_print_modalias(char *buf, int size, const struct input_dev *id)
+{
+	int full_len;
+
+	/*
+	 * Printing is done in 2 passes: first one figures out total length
+	 * needed for the modalias string, second one will try to trim key
+	 * data in case when buffer is too small for the entire modalias.
+	 * If the buffer is too small regardless, it will fill as much as it
+	 * can (without trimming key data) into the buffer and leave it to
+	 * the caller to figure out what to do with the result.
+	 */
+	full_len = input_print_modalias_parts(NULL, 0, 0, id);
+	return input_print_modalias_parts(buf, size, full_len, id);
+}
+
 static ssize_t input_dev_show_modalias(struct device *dev,
 				       struct device_attribute *attr,
 				       char *buf)
@@ -1429,7 +1482,9 @@ static ssize_t input_dev_show_modalias(struct device *dev,
 	struct input_dev *id = to_input_dev(dev);
 	ssize_t len;
 
-	len = input_print_modalias(buf, PAGE_SIZE, id, 1);
+	len = input_print_modalias(buf, PAGE_SIZE, id);
+	if (len < PAGE_SIZE - 2)
+		len += snprintf(buf + len, PAGE_SIZE - len, "\n");
 
 	return min_t(int, len, PAGE_SIZE);
 }
@@ -1641,6 +1696,23 @@ static int input_add_uevent_bm_var(struct kobj_uevent_env *env,
 	return 0;
 }
 
+/*
+ * This is a pretty gross hack. When building uevent data the driver core
+ * may try adding more environment variables to kobj_uevent_env without
+ * telling us, so we have no idea how much of the buffer we can use to
+ * avoid overflows/-ENOMEM elsewhere. To work around this let's artificially
+ * reduce amount of memory we will use for the modalias environment variable.
+ *
+ * The potential additions are:
+ *
+ * SEQNUM=18446744073709551615 - (%llu - 28 bytes)
+ * HOME=/ (6 bytes)
+ * PATH=/sbin:/bin:/usr/sbin:/usr/bin (34 bytes)
+ *
+ * 68 bytes total. Allow extra buffer - 96 bytes
+ */
+#define UEVENT_ENV_EXTRA_LEN	96
+
 static int input_add_uevent_modalias_var(struct kobj_uevent_env *env,
 					 const struct input_dev *dev)
 {
@@ -1650,9 +1722,11 @@ static int input_add_uevent_modalias_var(struct kobj_uevent_env *env,
 		return -ENOMEM;
 
 	len = input_print_modalias(&env->buf[env->buflen - 1],
-				   sizeof(env->buf) - env->buflen,
-				   dev, 0);
-	if (len >= (sizeof(env->buf) - env->buflen))
+				   (int)sizeof(env->buf) - env->buflen -
+					UEVENT_ENV_EXTRA_LEN,
+				   dev);
+	if (len >= ((int)sizeof(env->buf) - env->buflen -
+					UEVENT_ENV_EXTRA_LEN))
 		return -ENOMEM;
 
 	env->buflen += len;