From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: [PATCH bpf] bpf: add bpf_jit_limit knob to restrict unpriv allocations Date: Thu, 25 Oct 2018 17:17:13 -0700 Message-ID: <20181026001711.w55n5au2vx3sepmb@ast-mbp> References: <20181022231104.3443-1-daniel@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ast@kernel.org, rick.p.edgecombe@intel.com, eric.dumazet@gmail.com, jannh@google.com, keescook@chromium.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Daniel Borkmann Return-path: Content-Disposition: inline In-Reply-To: <20181022231104.3443-1-daniel@iogearbox.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, Oct 23, 2018 at 01:11:04AM +0200, Daniel Borkmann wrote: > Rick reported that the BPF JIT could potentially fill the entire module > space with BPF programs from unprivileged users which would prevent later > attempts to load normal kernel modules or privileged BPF programs, for > example. If JIT was enabled but unsuccessful to generate the image, then > before commit 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") > we would always fall back to the BPF interpreter. Nowadays in the case > where the CONFIG_BPF_JIT_ALWAYS_ON could be set, then the load will abort > with a failure since the BPF interpreter was compiled out. > > Add a global limit and enforce it for unprivileged users such that in case > of BPF interpreter compiled out we fail once the limit has been reached > or we fall back to BPF interpreter earlier w/o using module mem if latter > was compiled in. In a next step, fair share among unprivileged users can > be resolved in particular for the case where we would fail hard once limit > is reached. > > Fixes: 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") > Fixes: 0a14842f5a3c ("net: filter: Just In Time compiler for x86-64") > Co-Developed-by: Rick Edgecombe > Signed-off-by: Daniel Borkmann > Acked-by: Alexei Starovoitov > Cc: Eric Dumazet > Cc: Jann Horn > Cc: Kees Cook > Cc: LKML > --- > Hi Rick, I've reworked the original patch into something much simpler > which is only focussing on the actual main issue we want to resolve right > now as a first step to make some forward progress, that is, limiting usage > on the JIT for unprivileged users. Tested the below on x86 and arm64. > (Trimmed down massive Cc list as well a bit and Cc'ed people related to > commits referenced and netdev where BPF patches are usually discussed.) > Thanks a lot! Applied to bpf tree. Thanks Daniel.