[PATCH v3] Bluetooth: L2CAP: Fix ECRED reconf rsp channel teardown race

Feng Ning
2026-04-15T03:23:31Z

The ECRED reconfiguration response tears down all channels that were part
of a failed procedure. The handler iterates over conn->chan_l while
holding conn->lock but l2cap_chan_hold() is called without first checking
whether the reference count has already reached zero. A concurrent path
(socket close, timer expiry) may drop the final reference outside
conn->lock, causing a use-after-free when the response is handled.

Replace l2cap_chan_hold() with l2cap_chan_hold_unless_zero() so that
channels whose reference count has already been dropped are skipped
safely. Add lockdep_assert_held(&conn->lock) to document the calling
requirements.

Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Feng Ning <feng@innora.ai>
---
net/bluetooth/l2cap_core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 77dec104a..191c38b4d 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -5466,6 +5466,8 @@ static inline int l2cap_ecred_reconf_rsp(struct l2cap_conn *conn,

BT_DBG("result 0x%4.4x", result);

+ lockdep_assert_held(&conn->lock);
+
if (!result)
return 0;

@@ -5473,7 +5475,9 @@ static inline int l2cap_ecred_reconf_rsp(struct l2cap_conn *conn,
if (chan->ident != cmd->ident)
continue;

- l2cap_chan_hold(chan);
+ if (!l2cap_chan_hold_unless_zero(chan))
+ continue;
+
l2cap_chan_lock(chan);

l2cap_chan_del(chan, ECONNRESET);
--
2.49.0