From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
To: nhorman@tuxdriver.com
Cc: davem@davemloft.net,
Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Christian Brauner <brauner@kernel.org>,
Stanislav Fomichev <sdf@google.com>,
Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
Xin Long <lucien.xin@gmail.com>,
linux-sctp@vger.kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org
Subject: [PATCH net-next v2] sctp: add bpf_bypass_getsockopt proto callback
Date: Thu, 11 May 2023 14:31:48 +0200 [thread overview]
Message-ID: <20230511123148.332043-1-aleksandr.mikhalitsyn@canonical.com> (raw)
Add bpf_bypass_getsockopt proto callback and filter out
SCTP_SOCKOPT_PEELOFF and SCTP_SOCKOPT_PEELOFF_FLAGS socket options
from running eBPF hook on them.
These options do fd_install(), and if BPF_CGROUP_RUN_PROG_GETSOCKOPT
hook returns an error after success of the original handler
sctp_getsockopt(...), userspace will receive an error from getsockopt
syscall and will be not aware that fd was successfully installed into fdtable.
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@canonical.com/
Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: linux-sctp@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Suggested-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
net/sctp/socket.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index cda8c2874691..a211a203003c 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8281,6 +8281,35 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname,
return retval;
}
+static bool sctp_bpf_bypass_getsockopt(int level, int optname)
+{
+ if (level == SOL_SCTP) {
+ switch (optname) {
+ /*
+ * These options do fd_install(), and if BPF_CGROUP_RUN_PROG_GETSOCKOPT
+ * hook returns an error after success of the original handler
+ * sctp_getsockopt(...), userspace will receive an error from getsockopt
+ * syscall and will be not aware that fd was successfully installed into fdtable.
+ *
+ * Let's prevent bpf cgroup hook from running on them.
+ */
+ case SCTP_SOCKOPT_PEELOFF:
+ case SCTP_SOCKOPT_PEELOFF_FLAGS:
+ /*
+ * As pointed by Marcelo Ricardo Leitner it seems reasonable to skip
+ * bpf getsockopt hook for this sockopt too. Because internaly, it
+ * triggers connect() and if error will be masked userspace can be confused.
+ */
+ case SCTP_SOCKOPT_CONNECTX3:
+ return true;
+ default:
+ return false;
+ }
+ }
+
+ return false;
+}
+
static int sctp_hash(struct sock *sk)
{
/* STUB */
@@ -9650,6 +9679,7 @@ struct proto sctp_prot = {
.shutdown = sctp_shutdown,
.setsockopt = sctp_setsockopt,
.getsockopt = sctp_getsockopt,
+ .bpf_bypass_getsockopt = sctp_bpf_bypass_getsockopt,
.sendmsg = sctp_sendmsg,
.recvmsg = sctp_recvmsg,
.bind = sctp_bind,
@@ -9705,6 +9735,7 @@ struct proto sctpv6_prot = {
.shutdown = sctp_shutdown,
.setsockopt = sctp_setsockopt,
.getsockopt = sctp_getsockopt,
+ .bpf_bypass_getsockopt = sctp_bpf_bypass_getsockopt,
.sendmsg = sctp_sendmsg,
.recvmsg = sctp_recvmsg,
.bind = sctp_bind,
--
2.34.1
next reply other threads:[~2023-05-11 12:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 12:31 Alexander Mikhalitsyn [this message]
2023-05-11 13:12 ` [PATCH net-next v2] sctp: add bpf_bypass_getsockopt proto callback Marcelo Ricardo Leitner
2023-05-11 13:26 ` Aleksandr Mikhalitsyn
-- strict thread matches above, loose matches on Subject: below --
2023-05-10 14:42 Alexander Mikhalitsyn
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