[PATCH 2/6] seccomp: make underlying bpf ref counted as well

Tycho Andersen
2015-09-04T16:07:14Z

In the next patch, we're going to add a way to access the underlying
filters via bpf fds. This means that we need to ref-count both the
struct seccomp_filter objects and the struct bpf_prog objects separately,
in case a process dies but a filter is still referred to by another
process.

Additionally, we mark classic converted seccomp filters as seccomp eBPF
programs, since they are a subset of what is supported in seccomp eBPF.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
CC: Kees Cook <keescook@chromium.org>
CC: Will Drewry <wad@chromium.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Serge E. Hallyn <serge.hallyn@ubuntu.com>
CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>
---
kernel/seccomp.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 5bd4779..acfe1fb 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -377,6 +377,8 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
}

atomic_set(&sfilter->usage, 1);
+ atomic_set(&sfilter->prog->aux->refcnt, 1);
+ sfilter->prog->type = BPF_PROG_TYPE_SECCOMP;

return sfilter;
}
@@ -469,7 +471,7 @@ void get_seccomp_filter(struct task_struct *tsk)
static inline void seccomp_filter_free(struct seccomp_filter *filter)
{
if (filter) {
- bpf_prog_free(filter->prog);
+ bpf_prog_put(filter->prog);
kfree(filter);
}
}
--
2.1.4