[PATCH 6.4 661/800] sctp: fix potential deadlock on &net->sctp.addr_wq_lock

Greg Kroah-Hartman
2023-07-16T20:25:08Z

From: Chengfeng Ye <dg573847474@gmail.com>

[ Upstream commit 6feb37b3b06e9049e20dcf7e23998f92c9c5be9a ]

As &net->sctp.addr_wq_lock is also acquired by the timer
sctp_addr_wq_timeout_handler() in protocal.c, the same lock acquisition
at sctp_auto_asconf_init() seems should disable irq since it is called
from sctp_accept() under process context.

Possible deadlock scenario:
sctp_accept()
-> sctp_sock_migrate()
-> sctp_auto_asconf_init()
-> spin_lock(&net->sctp.addr_wq_lock)
<timer interrupt>
-> sctp_addr_wq_timeout_handler()
-> spin_lock_bh(&net->sctp.addr_wq_lock); (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

The tentative patch fix the potential deadlock by spin_lock_bh().

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Fixes: 34e5b0118685 ("sctp: delay auto_asconf init until binding the first addr")
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/20230627120340.19432-1-dg573847474@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sctp/socket.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index a68e1d541b128..ee15eff6364ee 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -364,9 +364,9 @@ static void sctp_auto_asconf_init(struct sctp_sock *sp)
struct net *net = sock_net(&sp->inet.sk);

if (net->sctp.default_auto_asconf) {
- spin_lock(&net->sctp.addr_wq_lock);
+ spin_lock_bh(&net->sctp.addr_wq_lock);
list_add_tail(&sp->auto_asconf_list, &net->sctp.auto_asconf_splist);
- spin_unlock(&net->sctp.addr_wq_lock);
+ spin_unlock_bh(&net->sctp.addr_wq_lock);
sp->do_auto_asconf = 1;
}
}
--
2.39.2