[PATCH 3.16 138/192] Bluetooth: Properly check L2CAP config option output buffer length

Ben Hutchings
2017-10-09T13:15:08Z

From: Ben Seri <ben@armis.com>

commit e860d2c904d1a9f38a24eb44c9f34b8f915a6ea3 upstream.

Validate the output buffer length for L2CAP config requests and responses
to avoid overflowing the stack buffer used for building the option blocks.

Signed-off-by: Ben Seri <ben@armis.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/bluetooth/l2cap_core.c | 80 +++++++++++++++++++++++++---------------------
1 file changed, 43 insertions(+), 37 deletions(-)

--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -59,7 +59,7 @@ static struct sk_buff *l2cap_build_cmd(s
u8 code, u8 ident, u16 dlen, void *data);
static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
void *data);
-static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data);
+static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data_size);
static void l2cap_send_disconn_req(struct l2cap_chan *chan, int err);

static void l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
@@ -1401,7 +1401,7 @@ static void l2cap_conn_start(struct l2ca

set_bit(CONF_REQ_SENT, &chan->conf_state);
l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf), buf);
+ l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
chan->num_conf_req++;
}

@@ -2978,12 +2978,15 @@ static inline int l2cap_get_conf_opt(voi
return len;
}

-static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val)
+static void l2cap_add_conf_opt(void **ptr, u8 type, u8 len, unsigned long val, size_t size)
{
struct l2cap_conf_opt *opt = *ptr;

BT_DBG("type 0x%2.2x len %u val 0x%lx", type, len, val);

+ if (size < L2CAP_CONF_OPT_SIZE + len)
+ return;
+
opt->type = type;
opt->len = len;

@@ -3008,7 +3011,7 @@ static void l2cap_add_conf_opt(void **pt
*ptr += L2CAP_CONF_OPT_SIZE + len;
}

-static void l2cap_add_opt_efs(void **ptr, struct l2cap_chan *chan)
+static void l2cap_add_opt_efs(void **ptr, struct l2cap_chan *chan, size_t size)
{
struct l2cap_conf_efs efs;

@@ -3036,7 +3039,7 @@ static void l2cap_add_opt_efs(void **ptr
}

l2cap_add_conf_opt(ptr, L2CAP_CONF_EFS, sizeof(efs),
- (unsigned long) &efs);
+ (unsigned long) &efs, size);
}

static void l2cap_ack_timeout(struct work_struct *work)
@@ -3180,11 +3183,12 @@ static inline void l2cap_txwin_setup(str
chan->ack_win = chan->tx_win;
}

-static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data)
+static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data, size_t data_size)
{
struct l2cap_conf_req *req = data;
struct l2cap_conf_rfc rfc = { .mode = chan->mode };
void *ptr = req->data;
+ void *endptr = data + data_size;
u16 size;

BT_DBG("chan %p", chan);
@@ -3209,7 +3213,7 @@ static int l2cap_build_conf_req(struct l

done:
if (chan->imtu != L2CAP_DEFAULT_MTU)
- l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);
+ l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, endptr - ptr);

switch (chan->mode) {
case L2CAP_MODE_BASIC:
@@ -3225,7 +3229,7 @@ done:
rfc.max_pdu_size = 0;

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
- (unsigned long) &rfc);
+ (unsigned long) &rfc, endptr - ptr);
break;

case L2CAP_MODE_ERTM:
@@ -3245,21 +3249,21 @@ done:
L2CAP_DEFAULT_TX_WINDOW);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
- (unsigned long) &rfc);
+ (unsigned long) &rfc, endptr - ptr);

if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
- l2cap_add_opt_efs(&ptr, chan);
+ l2cap_add_opt_efs(&ptr, chan, endptr - ptr);

if (test_bit(FLAG_EXT_CTRL, &chan->flags))
l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
- chan->tx_win);
+ chan->tx_win, endptr - ptr);

if (chan->conn->feat_mask & L2CAP_FEAT_FCS)
if (chan->fcs == L2CAP_FCS_NONE ||
test_bit(CONF_RECV_NO_FCS, &chan->conf_state)) {
chan->fcs = L2CAP_FCS_NONE;
l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1,
- chan->fcs);
+ chan->fcs, endptr - ptr);
}
break;

@@ -3277,17 +3281,17 @@ done:
rfc.max_pdu_size = cpu_to_le16(size);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
- (unsigned long) &rfc);
+ (unsigned long) &rfc, endptr - ptr);

if (test_bit(FLAG_EFS_ENABLE, &chan->flags))
- l2cap_add_opt_efs(&ptr, chan);
+ l2cap_add_opt_efs(&ptr, chan, endptr - ptr);

if (chan->conn->feat_mask & L2CAP_FEAT_FCS)
if (chan->fcs == L2CAP_FCS_NONE ||
test_bit(CONF_RECV_NO_FCS, &chan->conf_state)) {
chan->fcs = L2CAP_FCS_NONE;
l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1,
- chan->fcs);
+ chan->fcs, endptr - ptr);
}
break;
}
@@ -3298,10 +3302,11 @@ done:
return ptr - data;
}

-static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data)
+static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data_size)
{
struct l2cap_conf_rsp *rsp = data;
void *ptr = rsp->data;
+ void *endptr = data + data_size;
void *req = chan->conf_req;
int len = chan->conf_len;
int type, hint, olen;
@@ -3403,7 +3408,7 @@ done:
return -ECONNREFUSED;

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
- (unsigned long) &rfc);
+ (unsigned long) &rfc, endptr - ptr);
}

if (result == L2CAP_CONF_SUCCESS) {
@@ -3416,7 +3421,7 @@ done:
chan->omtu = mtu;
set_bit(CONF_MTU_DONE, &chan->conf_state);
}
- l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->omtu);
+ l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->omtu, endptr - ptr);

if (remote_efs) {
if (chan->local_stype != L2CAP_SERV_NOTRAFIC &&
@@ -3430,7 +3435,7 @@ done:

l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
sizeof(efs),
- (unsigned long) &efs);
+ (unsigned long) &efs, endptr - ptr);
} else {
/* Send PENDING Conf Rsp */
result = L2CAP_CONF_PENDING;
@@ -3463,7 +3468,7 @@ done:
set_bit(CONF_MODE_DONE, &chan->conf_state);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
- sizeof(rfc), (unsigned long) &rfc);
+ sizeof(rfc), (unsigned long) &rfc, endptr - ptr);

if (test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
chan->remote_id = efs.id;
@@ -3477,7 +3482,7 @@ done:
le32_to_cpu(efs.sdu_itime);
l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS,
sizeof(efs),
- (unsigned long) &efs);
+ (unsigned long) &efs, endptr - ptr);
}
break;

@@ -3491,7 +3496,7 @@ done:
set_bit(CONF_MODE_DONE, &chan->conf_state);

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC, sizeof(rfc),
- (unsigned long) &rfc);
+ (unsigned long) &rfc, endptr - ptr);

break;

@@ -3513,10 +3518,11 @@ done:
}

static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
- void *data, u16 *result)
+ void *data, size_t size, u16 *result)
{
struct l2cap_conf_req *req = data;
void *ptr = req->data;
+ void *endptr = data + size;
int type, olen;
unsigned long val;
struct l2cap_conf_rfc rfc = { .mode = L2CAP_MODE_BASIC };
@@ -3534,13 +3540,13 @@ static int l2cap_parse_conf_rsp(struct l
chan->imtu = L2CAP_DEFAULT_MIN_MTU;
} else
chan->imtu = val;
- l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu);
+ l2cap_add_conf_opt(&ptr, L2CAP_CONF_MTU, 2, chan->imtu, endptr - ptr);
break;

case L2CAP_CONF_FLUSH_TO:
chan->flush_to = val;
l2cap_add_conf_opt(&ptr, L2CAP_CONF_FLUSH_TO,
- 2, chan->flush_to);
+ 2, chan->flush_to, endptr - ptr);
break;

case L2CAP_CONF_RFC:
@@ -3554,13 +3560,13 @@ static int l2cap_parse_conf_rsp(struct l
chan->fcs = 0;

l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
- sizeof(rfc), (unsigned long) &rfc);
+ sizeof(rfc), (unsigned long) &rfc, endptr - ptr);
break;

case L2CAP_CONF_EWS:
chan->ack_win = min_t(u16, val, chan->ack_win);
l2cap_add_conf_opt(&ptr, L2CAP_CONF_EWS, 2,
- chan->tx_win);
+ chan->tx_win, endptr - ptr);
break;

case L2CAP_CONF_EFS:
@@ -3573,7 +3579,7 @@ static int l2cap_parse_conf_rsp(struct l
return -ECONNREFUSED;

l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs),
- (unsigned long) &efs);
+ (unsigned long) &efs, endptr - ptr);
break;

case L2CAP_CONF_FCS:
@@ -3678,7 +3684,7 @@ void __l2cap_connect_rsp_defer(struct l2
return;

l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf), buf);
+ l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
chan->num_conf_req++;
}

@@ -3885,7 +3891,7 @@ sendresp:
u8 buf[128];
set_bit(CONF_REQ_SENT, &chan->conf_state);
l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf), buf);
+ l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
chan->num_conf_req++;
}

@@ -3965,7 +3971,7 @@ static int l2cap_connect_create_rsp(stru
break;

l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, req), req);
+ l2cap_build_conf_req(chan, req, sizeof(req)), req);
chan->num_conf_req++;
break;

@@ -4077,7 +4083,7 @@ static inline int l2cap_config_req(struc
}

/* Complete config. */
- len = l2cap_parse_conf_req(chan, rsp);
+ len = l2cap_parse_conf_req(chan, rsp, sizeof(rsp));
if (len < 0) {
l2cap_send_disconn_req(chan, ECONNRESET);
goto unlock;
@@ -4111,7 +4117,7 @@ static inline int l2cap_config_req(struc
if (!test_and_set_bit(CONF_REQ_SENT, &chan->conf_state)) {
u8 buf[64];
l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf), buf);
+ l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
chan->num_conf_req++;
}

@@ -4171,7 +4177,7 @@ static inline int l2cap_config_rsp(struc
char buf[64];

len = l2cap_parse_conf_rsp(chan, rsp->data, len,
- buf, &result);
+ buf, sizeof(buf), &result);
if (len < 0) {
l2cap_send_disconn_req(chan, ECONNRESET);
goto done;
@@ -4201,7 +4207,7 @@ static inline int l2cap_config_rsp(struc
/* throw out any old stored conf requests */
result = L2CAP_CONF_SUCCESS;
len = l2cap_parse_conf_rsp(chan, rsp->data, len,
- req, &result);
+ req, sizeof(req), &result);
if (len < 0) {
l2cap_send_disconn_req(chan, ECONNRESET);
goto done;
@@ -4782,7 +4788,7 @@ static void l2cap_do_create(struct l2cap
set_bit(CONF_REQ_SENT, &chan->conf_state);
l2cap_send_cmd(chan->conn, l2cap_get_ident(chan->conn),
L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf), buf);
+ l2cap_build_conf_req(chan, buf, sizeof(buf)), buf);
chan->num_conf_req++;
}
}
@@ -7361,7 +7367,7 @@ int l2cap_security_cfm(struct hci_conn *
set_bit(CONF_REQ_SENT, &chan->conf_state);
l2cap_send_cmd(conn, l2cap_get_ident(conn),
L2CAP_CONF_REQ,
- l2cap_build_conf_req(chan, buf),
+ l2cap_build_conf_req(chan, buf, sizeof(buf)),
buf);
chan->num_conf_req++;
}