Subject: Re: [syzbot] KASAN: slab-out-of-bounds Read in hci_le_meta_evt (2)

From: Pavel Skripkin <[email-masked]>
Date: Sun, 31 Oct 2021 23:16:12 +0300

On 10/31/21 21:49, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> 
> Reported-and-tested-by: [email-masked]
> 
> Tested on:
> 
> commit:         180eca54 Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6362530af157355b
> dashboard link: https://syzkaller.appspot.com/bug?extid=e3fcb9c4f3c2a931dc40
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> patch:          https://syzkaller.appspot.com/x/patch.diff?x=1295a186b00000
> 
> Note: testing is done by a robot and is best-effort only.
> 

Ok, let's check more corner cases. Looks like nothing checks them.

#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

With regards,
Pavel Skripkin

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 0bca035bf2dc..50d1d62c15ec 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5780,7 +5780,8 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		struct hci_ev_le_advertising_info *ev = ptr;
 		s8 rssi;
 
-		if (ev->length <= HCI_MAX_AD_LENGTH) {
+		if (ev->length <= HCI_MAX_AD_LENGTH &&
+		    ev->data + ev->length <= skb_tail_pointer(skb)) {
 			rssi = ev->data[ev->length];
 			process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
 					   ev->bdaddr_type, NULL, 0, rssi,
@@ -5790,6 +5791,11 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		}
 
 		ptr += sizeof(*ev) + ev->length + 1;
+
+		if (ptr > (void *) skb_tail_pointer(skb) - sizeof(*ev)) {
+			bt_dev_err(hdev, "Malicious advertising data. Stopping processing");
+			break;
+		}
 	}
 
 	hci_dev_unlock(hdev);