[PATCH net 2/4] mptcp: fix scheduling with atomic in timestamp sockopt

[Matthieu Baerts (NGI0)]

From: Gang Yan <yangang@xxxxxxxxxx>

Using lock_sock_fast() (atomic context) around sock_set_timestamp()
and sock_set_timestamping() is unsafe, as both helpers can sleep.

Replace lock_sock_fast() with sleepable lock_sock()/release_sock()
to avoid scheduling while atomic panic.

Fixes: 9061f24bf82e ("mptcp: sockopt: propagate timestamp request to subflows")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/patchset/20260420093343.16443-1-gang.yan@xxxxxxxxx
Signed-off-by: Gang Yan <yangang@xxxxxxxxxx>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
---
 net/mptcp/sockopt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 79db15903e7a..0efe40be2fde 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -159,10 +159,10 @@ static int mptcp_setsockopt_sol_socket_tstamp(struct mptcp_sock *msk, int optnam
 	lock_sock(sk);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-		bool slow = lock_sock_fast(ssk);
 
+		lock_sock(ssk);
 		sock_set_timestamp(ssk, optname, !!val);
-		unlock_sock_fast(ssk, slow);
+		release_sock(ssk);
 	}
 
 	release_sock(sk);
@@ -235,10 +235,10 @@ static int mptcp_setsockopt_sol_socket_timestamping(struct mptcp_sock *msk,
 
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-		bool slow = lock_sock_fast(ssk);
 
+		lock_sock(ssk);
 		sock_set_timestamping(ssk, optname, timestamping);
-		unlock_sock_fast(ssk, slow);
+		release_sock(ssk);
 	}
 
 	release_sock(sk);

-- 
2.53.0