On Wed, May 10, 2023 at 6:15 AM Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> wrote: > > 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@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 > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> with a small nit below > --- > net/sctp/socket.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > index cda8c2874691..a9a0ababea90 100644 > --- a/net/sctp/socket.c > +++ b/net/sctp/socket.c > @@ -8281,6 +8281,29 @@ static int sctp_getsockopt(struct sock *sk, int level, int optname, > return retval; > } > [...] > +bool sctp_bpf_bypass_getsockopt(int level, int optname) static bool ... ? You're not making it indirect-callable, so seems fine to keep private to this compilation unit? > +{ > + /* > + * 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. > + */ > + if (level == SOL_SCTP) { > + switch (optname) { > + case SCTP_SOCKOPT_PEELOFF: > + case SCTP_SOCKOPT_PEELOFF_FLAGS: > + return true; > + default: > + return false; > + } > + } > + > + return false; > +} > + > static int sctp_hash(struct sock *sk) > { > /* STUB */ > @@ -9650,6 +9673,7 @@ 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 +9729,7 @@ 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 >
