From d0be8347c623e0ac4202a1d4e0373882821f56b0 Mon Sep 17 00:00:00 2001
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Date: Thu, 21 Jul 2022 09:10:50 -0700
Subject: [PATCH] Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put
Git-commit: d0be8347c623e0ac4202a1d4e0373882821f56b0
Patch-mainline: v5.19
References: git-fixes
This fixes the following trace which is caused by hci_rx_work starting up
*after* the final channel reference has been put() during sock_close() but
*before* the references to the channel have been destroyed, so instead
the code now rely on kref_get_unless_zero/l2cap_chan_hold_unless_zero to
prevent referencing a channel that is about to be destroyed.
refcount_t: increment on 0; use-after-free.
BUG: KASAN: use-after-free in refcount_dec_and_test+0x20/0xd0
Read of size 4 at addr ffffffc114f5bf18 by task kworker/u17:14/705
CPU: 4 PID: 705 Comm: kworker/u17:14 Tainted: G S W
4.14.234-00003-g1fb6d0bd49a4-dirty #28
Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150
Google Inc. MSM sm8150 Flame DVT (DT)
Workqueue: hci0 hci_rx_work
Call trace:
dump_backtrace+0x0/0x378
show_stack+0x20/0x2c
dump_stack+0x124/0x148
print_address_description+0x80/0x2e8
__kasan_report+0x168/0x188
kasan_report+0x10/0x18
__asan_load4+0x84/0x8c
refcount_dec_and_test+0x20/0xd0
l2cap_chan_put+0x48/0x12c
l2cap_recv_frame+0x4770/0x6550
l2cap_recv_acldata+0x44c/0x7a4
hci_acldata_packet+0x100/0x188
hci_rx_work+0x178/0x23c
process_one_work+0x35c/0x95c
worker_thread+0x4cc/0x960
kthread+0x1a8/0x1c4
ret_from_fork+0x10/0x18
Cc: stable@kernel.org
Reported-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Tested-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
include/net/bluetooth/l2cap.h | 1
net/bluetooth/l2cap_core.c | 61 +++++++++++++++++++++++++++++++++---------
2 files changed, 49 insertions(+), 13 deletions(-)
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -845,6 +845,7 @@ enum {
};
void l2cap_chan_hold(struct l2cap_chan *c);
+struct l2cap_chan *l2cap_chan_hold_unless_zero(struct l2cap_chan *c);
void l2cap_chan_put(struct l2cap_chan *c);
static inline void l2cap_chan_lock(struct l2cap_chan *chan)
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -111,7 +111,8 @@ static struct l2cap_chan *__l2cap_get_ch
}
/* Find channel with given SCID.
- * Returns locked channel. */
+ * Returns a reference locked channel.
+ */
static struct l2cap_chan *l2cap_get_chan_by_scid(struct l2cap_conn *conn,
u16 cid)
{
@@ -119,15 +120,19 @@ static struct l2cap_chan *l2cap_get_chan
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_scid(conn, cid);
- if (c)
- l2cap_chan_lock(c);
+ if (c) {
+ /* Only lock if chan reference is not 0 */
+ c = l2cap_chan_hold_unless_zero(c);
+ if (c)
+ l2cap_chan_lock(c);
+ }
mutex_unlock(&conn->chan_lock);
return c;
}
/* Find channel with given DCID.
- * Returns locked channel.
+ * Returns a reference locked channel.
*/
static struct l2cap_chan *l2cap_get_chan_by_dcid(struct l2cap_conn *conn,
u16 cid)
@@ -136,8 +141,12 @@ static struct l2cap_chan *l2cap_get_chan
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_dcid(conn, cid);
- if (c)
- l2cap_chan_lock(c);
+ if (c) {
+ /* Only lock if chan reference is not 0 */
+ c = l2cap_chan_hold_unless_zero(c);
+ if (c)
+ l2cap_chan_lock(c);
+ }
mutex_unlock(&conn->chan_lock);
return c;
@@ -162,8 +171,12 @@ static struct l2cap_chan *l2cap_get_chan
mutex_lock(&conn->chan_lock);
c = __l2cap_get_chan_by_ident(conn, ident);
- if (c)
- l2cap_chan_lock(c);
+ if (c) {
+ /* Only lock if chan reference is not 0 */
+ c = l2cap_chan_hold_unless_zero(c);
+ if (c)
+ l2cap_chan_lock(c);
+ }
mutex_unlock(&conn->chan_lock);
return c;
@@ -497,6 +510,16 @@ void l2cap_chan_hold(struct l2cap_chan *
kref_get(&c->kref);
}
+struct l2cap_chan *l2cap_chan_hold_unless_zero(struct l2cap_chan *c)
+{
+ BT_DBG("chan %p orig refcnt %u", c, kref_read(&c->kref));
+
+ if (!kref_get_unless_zero(&c->kref))
+ return NULL;
+
+ return c;
+}
+
void l2cap_chan_put(struct l2cap_chan *c)
{
BT_DBG("chan %p orig refcnt %d", c, kref_read(&c->kref));
@@ -1964,7 +1987,10 @@ static struct l2cap_chan *l2cap_global_c
src_match = !bacmp(&c->src, src);
dst_match = !bacmp(&c->dst, dst);
if (src_match && dst_match) {
- l2cap_chan_hold(c);
+ c = l2cap_chan_hold_unless_zero(c);
+ if (!c)
+ continue;
+
read_unlock(&chan_list_lock);
return c;
}
@@ -1979,7 +2005,7 @@ static struct l2cap_chan *l2cap_global_c
}
if (c1)
- l2cap_chan_hold(c1);
+ c1 = l2cap_chan_hold_unless_zero(c1);
read_unlock(&chan_list_lock);
@@ -4459,6 +4485,7 @@ static inline int l2cap_config_req(struc
unlock:
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return err;
}
@@ -4572,6 +4599,7 @@ static inline int l2cap_config_rsp(struc
done:
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return err;
}
@@ -5299,6 +5327,7 @@ send_move_response:
l2cap_send_move_chan_rsp(chan, result);
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return 0;
}
@@ -5391,6 +5420,7 @@ static void l2cap_move_continue(struct l
}
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
}
static void l2cap_move_fail(struct l2cap_conn *conn, u8 ident, u16 icid,
@@ -5420,6 +5450,7 @@ static void l2cap_move_fail(struct l2cap
l2cap_send_move_chan_cfm(chan, L2CAP_MC_UNCONFIRMED);
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
}
static int l2cap_move_channel_rsp(struct l2cap_conn *conn,
@@ -5483,6 +5514,7 @@ static int l2cap_move_channel_confirm(st
l2cap_send_move_chan_cfm_rsp(conn, cmd->ident, icid);
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return 0;
}
@@ -5518,6 +5550,7 @@ static inline int l2cap_move_channel_con
}
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return 0;
}
@@ -5890,12 +5923,11 @@ static inline int l2cap_le_credits(struc
if (credits > max_credits) {
BT_ERR("LE credits overflow");
l2cap_send_disconn_req(chan, ECONNRESET);
- l2cap_chan_unlock(chan);
/* Return 0 so that we don't trigger an unnecessary
* command reject packet.
*/
- return 0;
+ goto unlock;
}
chan->tx_credits += credits;
@@ -5906,7 +5938,9 @@ static inline int l2cap_le_credits(struc
if (chan->tx_credits)
chan->ops->resume(chan);
+unlock:
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return 0;
}
@@ -7586,6 +7620,7 @@ drop:
done:
l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
}
static void l2cap_conless_channel(struct l2cap_conn *conn, __le16 psm,
@@ -8073,7 +8108,7 @@ static struct l2cap_chan *l2cap_global_f
if (src_type != c->src_type)
continue;
- l2cap_chan_hold(c);
+ c = l2cap_chan_hold_unless_zero(c);
read_unlock(&chan_list_lock);
return c;
}