From: Yousef Alhouseen <alhouseenyousef@gmail.com> stable inclusion from stable-v5.10.261 commit c0577c55219be42b6ea2ea8db11e85bfab6f4e8d category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16697 CVE: CVE-2026-64406 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 4bd0b274054f2679f28b70222b607bb0afc3ab9a upstream. bt_accept_get() takes a temporary reference before dropping the accept queue lock. bt_accept_dequeue() currently drops that reference before bt_accept_unlink(), leaving only the queue reference. bt_accept_unlink() drops the queue reference. The subsequent sock_hold() therefore accesses freed memory if it was the final reference, as observed by KASAN during listening L2CAP socket cleanup. Retain the temporary queue-walk reference through unlink and hand it to the caller on success. Drop it explicitly on the closed and not-yet-connected paths. Fixes: ab1513597c6c ("Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del()") Reported-by: syzbot+674ff7e4d7fdfd572afc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=674ff7e4d7fdfd572afc Cc: stable@vger.kernel.org Signed-off-by: Yousef Alhouseen <alhouseenyousef@gmail.com> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Xia Fukun <xiafukun@huawei.com> --- net/bluetooth/af_bluetooth.c | 17 +++-------------- net/bluetooth/l2cap_sock.c | 4 ++-- 2 files changed, 5 insertions(+), 16 deletions(-) diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c index 64aa0199dd2f..449f32ead4a6 100644 --- a/net/bluetooth/af_bluetooth.c +++ b/net/bluetooth/af_bluetooth.c @@ -303,7 +303,7 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock) restart: for (sk = bt_accept_get(parent, NULL); sk; sk = next) { - /* Prevent early freeing of sk due to unlink and sock_kill */ + /* The reference from bt_accept_get() keeps sk alive. */ lock_sock(sk); /* Check sk has not already been unlinked via @@ -319,13 +319,11 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock) next = bt_accept_get(parent, sk); - /* sk is safely in the parent list so reduce reference count */ - sock_put(sk); - /* FIXME: Is this check still needed */ if (sk->sk_state == BT_CLOSED) { bt_accept_unlink(sk); release_sock(sk); + sock_put(sk); continue; } @@ -335,16 +333,6 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock) if (newsock) sock_graft(sk, newsock); - /* Hand the caller a reference taken while sk is - * still locked. bt_accept_unlink() just dropped - * the accept-queue reference; without this hold a - * concurrent teardown (e.g. l2cap_conn_del() -> - * l2cap_sock_kill()) could free sk between - * release_sock() and the caller using it. Every - * caller drops this with sock_put() when done. - */ - sock_hold(sk); - release_sock(sk); if (next) sock_put(next); @@ -352,6 +340,7 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock) } release_sock(sk); + sock_put(sk); } return NULL; diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index cc06be98f3c0..deb5b8fc8612 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1438,8 +1438,8 @@ static void l2cap_sock_cleanup_listen(struct sock *parent) /* Close not yet accepted channels. * - * bt_accept_dequeue() now returns sk with an extra reference held - * (taken while sk was still locked) so a concurrent l2cap_conn_del() + * bt_accept_dequeue() returns sk with its temporary queue-walk + * reference held, so a concurrent l2cap_conn_del() * -> l2cap_sock_kill() cannot free sk under us. * * cleanup_listen() runs under the parent sk lock, so unlike -- 2.34.1