[PATCH v3] Bluetooth: HIDP: fix missing length checks in hidp_input_report()

[Muhammad Bilal <meatuni001@gmail.com>]

hidp_input_report() reads keyboard and mouse payload data from an skb
without first verifying that skb->len contains enough data.

hidp_recv_intr_frame() pulls the 1-byte HIDP header before dispatching
to hidp_input_report(). If a paired device sends a truncated packet,
the handler reads beyond the valid skb data, resulting in an
out-of-bounds read of skb data. The OOB bytes may be interpreted as
phantom key presses or spurious mouse movement.

Replace the open-coded length tracking and pointer arithmetic with
skb_pull_data() calls. skb_pull_data() returns NULL if the requested
bytes are not present, eliminating the need for a manual size variable
and the separate skb->len guard.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
v3:
 - Replace manual length checks and pointer arithmetic with
   skb_pull_data() per Luiz's review
v2:
 - Add Cc: stable@vger.kernel.org per Greg KH's note
---
 net/bluetooth/hidp/core.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 976f91eeb..70344bd32 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -179,12 +179,21 @@ static void hidp_input_report(struct hidp_session *session, struct sk_buff *skb)
 {
 	struct input_dev *dev = session->input;
 	unsigned char *keys = session->keys;
-	unsigned char *udata = skb->data + 1;
-	signed char *sdata = skb->data + 1;
-	int i, size = skb->len - 1;
+	unsigned char *udata;
+	signed char *sdata;
+	u8 *hdr;
+	int i;
+
+	hdr = skb_pull_data(skb, 1);
+	if (!hdr)
+		return;
 
-	switch (skb->data[0]) {
+	switch (*hdr) {
 	case 0x01:	/* Keyboard report */
+		udata = skb_pull_data(skb, 8);
+		if (!udata)
+			break;
+
 		for (i = 0; i < 8; i++)
 			input_report_key(dev, hidp_keycode[i + 224], (udata[0] >> i) & 1);
 
@@ -213,6 +222,10 @@ static void hidp_input_report(struct hidp_session *session, struct sk_buff *skb)
 		break;
 
 	case 0x02:	/* Mouse report */
+		sdata = skb_pull_data(skb, 3);
+		if (!sdata)
+			break;
+
 		input_report_key(dev, BTN_LEFT,   sdata[0] & 0x01);
 		input_report_key(dev, BTN_RIGHT,  sdata[0] & 0x02);
 		input_report_key(dev, BTN_MIDDLE, sdata[0] & 0x04);
@@ -222,7 +235,7 @@ static void hidp_input_report(struct hidp_session *session, struct sk_buff *skb)
 		input_report_rel(dev, REL_X, sdata[1]);
 		input_report_rel(dev, REL_Y, sdata[2]);
 
-		if (size > 3)
+		if (skb->len > 0)
 			input_report_rel(dev, REL_WHEEL, sdata[3]);
 		break;
 	}
-- 
2.54.0