This is a note to let you know that I've just added the patch titled
sctp: add bpf_bypass_getsockopt proto callback
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sctp-add-bpf_bypass_getsockopt-proto-callback.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8af62ddacd308c1ce7f55cc8fdaa7d5a63fce756
Author: Alexander Mikhalitsyn <alexander@xxxxxxxxxxxxx>
Date: Thu May 11 15:25:06 2023 +0200
sctp: add bpf_bypass_getsockopt proto callback
[ Upstream commit 2598619e012cee5273a2821441b9a051ad931249 ]
Implement ->bpf_bypass_getsockopt proto callback and filter out
SCTP_SOCKOPT_PEELOFF, SCTP_SOCKOPT_PEELOFF_FLAGS and SCTP_SOCKOPT_CONNECTX3
socket options from running eBPF hook on them.
SCTP_SOCKOPT_PEELOFF and SCTP_SOCKOPT_PEELOFF_FLAGS 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 a fdtable.
As pointed by Marcelo Ricardo Leitner it seems reasonable to skip
bpf getsockopt hook for SCTP_SOCKOPT_CONNECTX3 sockopt too.
Because internaly, it triggers connect() and if error is masked
then userspace will be confused.
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/
Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Cc: Xin Long <lucien.xin@xxxxxxxxx>
Cc: linux-sctp@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Suggested-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
Acked-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 2bbc81ddb9e08..ed35d4a4c5253 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8287,6 +8287,22 @@ 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) {
+ case SCTP_SOCKOPT_PEELOFF:
+ case SCTP_SOCKOPT_PEELOFF_FLAGS:
+ case SCTP_SOCKOPT_CONNECTX3:
+ return true;
+ default:
+ return false;
+ }
+ }
+
+ return false;
+}
+
static int sctp_hash(struct sock *sk)
{
/* STUB */
@@ -9655,6 +9671,7 @@ 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,
@@ -9707,6 +9724,7 @@ 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,
