Bluetooth: MGMT: Fix OOB access in parse_adv_monitor_pattern()

In the parse_adv_monitor_pattern() function, the value of
the 'length' variable is currently limited to HCI_MAX_EXT_AD_LENGTH(251).
The size of the 'value' array in the mgmt_adv_pattern structure is 31.
If the value of 'pattern[i].length' is set in the user space
and exceeds 31, the 'patterns[i].value' array can be accessed
out of bound when copied.

Increasing the size of the 'value' array in
the 'mgmt_adv_pattern' structure will break the userspace.
Considering this, and to avoid OOB access revert the limits for 'offset'
and 'length' back to the value of HCI_MAX_AD_LENGTH.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: db08722 ("Bluetooth: hci_core: Fix missing instances using HCI_MAX_AD_LENGTH")
Cc: stable@vger.kernel.org
Signed-off-by: Ilia Gavrilov <Ilia.Gavrilov@infotecs.ru>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Author: Ilia Gavrilov

include/net/bluetooth/mgmt.h

@@ -780,7 +780,7 @@ struct mgmt_adv_pattern {
 	__u8 ad_type;
 	__u8 offset;
 	__u8 length;
-	__u8 value[31];
+	__u8 value[HCI_MAX_AD_LENGTH];
 } __packed;
 
 #define MGMT_OP_ADD_ADV_PATTERNS_MONITOR	0x0052

net/bluetooth/mgmt.c

@@ -5395,9 +5395,9 @@ static u8 parse_adv_monitor_pattern(struct adv_monitor *m, u8 pattern_count,
 	for (i = 0; i < pattern_count; i++) {
 		offset = patterns[i].offset;
 		length = patterns[i].length;
-		if (offset >= HCI_MAX_EXT_AD_LENGTH ||
-		    length > HCI_MAX_EXT_AD_LENGTH ||
-		    (offset + length) > HCI_MAX_EXT_AD_LENGTH)
+		if (offset >= HCI_MAX_AD_LENGTH ||
+		    length > HCI_MAX_AD_LENGTH ||
+		    (offset + length) > HCI_MAX_AD_LENGTH)
 			return MGMT_STATUS_INVALID_PARAMS;
 
 		p = kmalloc(sizeof(*p), GFP_KERNEL);