[PATCH net-next] net: core: add SOL_SOCKET filter for bpf getsockopt hook

[Alexander Mikhalitsyn]

We have per struct proto ->bpf_bypass_getsockopt callback
to filter out bpf socket cgroup getsockopt hook from being called.

It seems worthwhile to add analogical helper for SOL_SOCKET
level socket options. First user will be SO_PEERPIDFD.

This patch was born as a result of discussion around a new SCM_PIDFD interface:
https://lore.kernel.org/all/20230413133355.350571-3-aleksandr.mikhalitsyn@xxxxxxxxxxxxx/

Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Cc: bpf@xxxxxxxxxxxxxxx
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
---
 include/linux/bpf-cgroup.h | 8 +++++---
 include/net/sock.h         | 1 +
 net/core/sock.c            | 5 +++++
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 57e9e109257e..97d8a49b35bf 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -387,10 +387,12 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
 	int __ret = retval;						       \
 	if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) &&			       \
 	    cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))		       \
-		if (!(sock)->sk_prot->bpf_bypass_getsockopt ||		       \
-		    !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_bypass_getsockopt, \
+		if (((level != SOL_SOCKET) ||				       \
+		     !sock_bpf_bypass_getsockopt(level, optname)) &&	       \
+		    (!(sock)->sk_prot->bpf_bypass_getsockopt ||		       \
+		     !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_bypass_getsockopt, \
 					tcp_bpf_bypass_getsockopt,	       \
-					level, optname))		       \
+					level, optname)))		       \
 			__ret = __cgroup_bpf_run_filter_getsockopt(	       \
 				sock, level, optname, optval, optlen,	       \
 				max_optlen, retval);			       \
diff --git a/include/net/sock.h b/include/net/sock.h
index 8b7ed7167243..530d6d22f42d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1847,6 +1847,7 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		  sockptr_t optval, sockptr_t optlen);
 int sock_getsockopt(struct socket *sock, int level, int op,
 		    char __user *optval, int __user *optlen);
+bool sock_bpf_bypass_getsockopt(int level, int optname);
 int sock_gettstamp(struct socket *sock, void __user *userstamp,
 		   bool timeval, bool time32);
 struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
diff --git a/net/core/sock.c b/net/core/sock.c
index 5440e67bcfe3..194a423eb6e5 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1963,6 +1963,11 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 			     USER_SOCKPTR(optlen));
 }
 
+bool sock_bpf_bypass_getsockopt(int level, int optname)
+{
+	return false;
+}
+
 /*
  * Initialize an sk_lock.
  *
-- 
2.34.1