Re: [PATCH v2 4/5] seccomp: add a way to access filters via bpf fds
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2015-09-11 11:47:53
Also in:
lkml, netdev
On 09/11/2015 02:21 AM, Tycho Andersen wrote:
This patch adds a way for a process that is "real root" to access the seccomp filters of another process. The process first does a PTRACE_SECCOMP_GET_FILTER_FD to get an fd with that process' seccomp filter attached, and then iterates on this with PTRACE_SECCOMP_NEXT_FILTER using bpf(BPF_PROG_DUMP) to dump the actual program at each step. Signed-off-by: Tycho Andersen <redacted> CC: Kees Cook <redacted> CC: Will Drewry <wad@chromium.org> CC: Oleg Nesterov <oleg@redhat.com> CC: Andy Lutomirski <luto@amacapital.net> CC: Pavel Emelyanov <redacted> CC: Serge E. Hallyn <redacted> CC: Alexei Starovoitov <ast@kernel.org> CC: Daniel Borkmann <daniel@iogearbox.net>
[...]
quoted hunk ↗ jump to hunk
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 58ae9f4..ac3ed1c 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c@@ -506,6 +506,30 @@ struct bpf_prog *bpf_prog_get(u32 ufd) } EXPORT_SYMBOL_GPL(bpf_prog_get); +int bpf_prog_set(u32 ufd, struct bpf_prog *new) +{ + struct fd f; + struct bpf_prog *prog; + + f = fdget(ufd); + + prog = get_prog(f); + if (!IS_ERR(prog) && prog) + bpf_prog_put(prog); + + atomic_inc(&new->aux->refcnt); + f.file->private_data = new; + fdput(f); + return 0;
So in case get_prog() fails, and for example f.file is infact NULL, you assign the bpf prog then to ERR_PTR(-EBADF)'s private_data? :(
+}
+EXPORT_SYMBOL_GPL(bpf_prog_set);
+
+int bpf_new_fd(struct bpf_prog *prog, int flags)
+{
+ return anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, flags);
+}
+EXPORT_SYMBOL_GPL(bpf_new_fd);Any reason why these two need to be exported for modules? Which modules are using them? I think modules should probably not mess with this. If you already name it generic, it would also be good if bpf_new_fd() is used in case of maps that call anon_inode_getfd(), too.