Messages in this thread | | | Subject | Re: [PATCH net-next] modules: allow modprobe load regular elf binaries | From | Alexei Starovoitov <> | Date | Fri, 9 Mar 2018 10:58:06 -0800 |
| |
On 3/9/18 10:50 AM, Linus Torvalds wrote: > On Fri, Mar 9, 2018 at 10:43 AM, Kees Cook <keescook@chromium.org> wrote: >> >> Module loading (via kernel_read_file()) already uses >> deny_write_access(), and so does do_open_execat(). As long as module >> loading doesn't call allow_write_access() before the execve() has >> started in the new implementation, I think we'd be covered here. > > No. kernel_read_file() only does it *during* the read. > > So there's a huge big honking gap between the two. > > Also, the second part of my suggestion was to be entirely synchronous > with the whole execution of the process, and do it within the "we do > mutual exclusion fo rmodules with the same name" logic. > > Note that Andrei's patch uses UMH_WAIT_EXEC. That's basically > "vfork+exec" - it only waits for the exec to have started, it doesn't > wait for the whole thing.
It's not waiting for the whole thing, because once bpfilter starts it stays running/sleeping because it's stateful. It needs normal malloc-ed memory to keep the state of iptable->bpf translation that it will use later during subsequent translation calls. Theoretically it can use bpf maps pinned in kernel memory to keep this state, but then it's non-swappable. It's better to keep bpfilter state in its own user memory.
| |