From: Xin Long <lucien.xin@xxxxxxxxx>
[ Upstream commit 82cb4e4612c633a9ce320e1773114875604a3cce ]
syzbot found a crash in tipc_topsrv_accept:
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
Workqueue: tipc_rcv tipc_topsrv_accept
RIP: 0010:kernel_accept+0x22d/0x350 net/socket.c:3487
Call Trace:
<TASK>
tipc_topsrv_accept+0x197/0x280 net/tipc/topsrv.c:460
process_one_work+0x991/0x1610 kernel/workqueue.c:2289
worker_thread+0x665/0x1080 kernel/workqueue.c:2436
kthread+0x2e4/0x3a0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
It was caused by srv->listener that might be set to null by
tipc_topsrv_stop() in net .exit whereas it's still used in
tipc_topsrv_accept() worker.
srv->listener is protected by srv->idr_lock in tipc_topsrv_stop(), so add
a check for srv->listener under srv->idr_lock in tipc_topsrv_accept() to
avoid the null-ptr-deref. To ensure the lsock is not released during the
tipc_topsrv_accept(), move sock_release() after tipc_topsrv_work_stop()
where it's waiting until the tipc_topsrv_accept worker to be done.
Note that sk_callback_lock is used to protect sk->sk_user_data instead of
srv->listener, and it should check srv in tipc_topsrv_listener_data_ready()
instead. This also ensures that no more tipc_topsrv_accept worker will be
started after tipc_conn_close() is called in tipc_topsrv_stop() where it
sets sk->sk_user_data to null.
Fixes: 0ef897be12b8 ("tipc: separate topology server listener socket from subcsriber sockets")
Reported-by: syzbot+c5ce866a8d30f4be0651@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: Jon Maloy <jmaloy@xxxxxxxxxx>
Link: https://lore.kernel.org/r/4eee264380c409c61c6451af1059b7fb271a7e7b.1666120790.git.lucien.xin@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/tipc/topsrv.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
index b8797ff153e6..1c5319678f28 100644
--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -450,12 +450,19 @@ static void tipc_conn_data_ready(struct sock *sk)
static void tipc_topsrv_accept(struct work_struct *work)
{
struct tipc_topsrv *srv = container_of(work, struct tipc_topsrv, awork);
- struct socket *lsock = srv->listener;
- struct socket *newsock;
+ struct socket *newsock, *lsock;
struct tipc_conn *con;
struct sock *newsk;
int ret;
+ spin_lock_bh(&srv->idr_lock);
+ if (!srv->listener) {
+ spin_unlock_bh(&srv->idr_lock);
+ return;
+ }
+ lsock = srv->listener;
+ spin_unlock_bh(&srv->idr_lock);
+
while (1) {
ret = kernel_accept(lsock, &newsock, O_NONBLOCK);
if (ret < 0)
@@ -489,7 +496,7 @@ static void tipc_topsrv_listener_data_ready(struct sock *sk)
read_lock_bh(&sk->sk_callback_lock);
srv = sk->sk_user_data;
- if (srv->listener)
+ if (srv)
queue_work(srv->rcv_wq, &srv->awork);
read_unlock_bh(&sk->sk_callback_lock);
}
@@ -699,8 +706,9 @@ static void tipc_topsrv_stop(struct net *net)
__module_get(lsock->sk->sk_prot_creator->owner);
srv->listener = NULL;
spin_unlock_bh(&srv->idr_lock);
- sock_release(lsock);
+
tipc_topsrv_work_stop(srv);
+ sock_release(lsock);
idr_destroy(&srv->conn_idr);
kfree(srv);
}
--
2.35.1
