From 5d6b58c932ec451a5c41482790eb5b1ecf165a94 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 2 Sep 2025 18:36:03 +0000 Subject: net: lockless sock_i_ino() Followup of commit c51da3f7a161 ("net: remove sock_i_uid()") A recent syzbot report was the trigger for this change. Over the years, we had many problems caused by the read_lock[_bh](&sk->sk_callback_lock) in sock_i_uid(). We could fix smc_diag_dump_proto() or make a more radical move: Instead of waiting for new syzbot reports, cache the socket inode number in sk->sk_ino, so that we no longer need to acquire sk->sk_callback_lock in sock_i_ino(). This makes socket dumps faster (one less cache line miss, and two atomic ops avoided). Prior art: commit 25a9c8a4431c ("netlink: Add __sock_i_ino() for __netlink_diag_dump().") commit 4f9bf2a2f5aa ("tcp: Don't acquire inet_listen_hashbucket::lock with disabled BH.") commit efc3dbc37412 ("rds: Make rds_sock_lock BH rather than IRQ safe.") Fixes: d2d6422f8bd1 ("x86: Allow to enable PREEMPT_RT.") Reported-by: syzbot+50603c05bbdf4dfdaffa@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/68b73804.050a0220.3db4df.01d8.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Reviewed-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20250902183603.740428-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- net/core/sock.c | 22 ---------------------- 1 file changed, 22 deletions(-) (limited to 'net/core/sock.c') diff --git a/net/core/sock.c b/net/core/sock.c index 7c26ec8dce63..158bddd23134 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2780,28 +2780,6 @@ void sock_pfree(struct sk_buff *skb) EXPORT_SYMBOL(sock_pfree); #endif /* CONFIG_INET */ -unsigned long __sock_i_ino(struct sock *sk) -{ - unsigned long ino; - - read_lock(&sk->sk_callback_lock); - ino = sk->sk_socket ? SOCK_INODE(sk->sk_socket)->i_ino : 0; - read_unlock(&sk->sk_callback_lock); - return ino; -} -EXPORT_SYMBOL(__sock_i_ino); - -unsigned long sock_i_ino(struct sock *sk) -{ - unsigned long ino; - - local_bh_disable(); - ino = __sock_i_ino(sk); - local_bh_enable(); - return ino; -} -EXPORT_SYMBOL(sock_i_ino); - /* * Allocate a skb from the socket's send buffer. */ -- cgit v1.2.3