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Mon, 09 Jul 2018 16:01:02 -0700 (PDT) Date: Mon, 9 Jul 2018 16:01:01 -0700 From: Alexei Starovoitov To: Tobias Tefke Cc: tobias.tefke@tutanota.com, ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] bpf: remove unnecessary condition in bpf_check() Message-ID: <20180709230059.p6afqogzp6rb4ka4@ast-mbp.dhcp.thefacebook.com> References: <20180709114837.23864-1-tobias.tefke@tutanota.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180709114837.23864-1-tobias.tefke@tutanota.com> User-Agent: NeoMutt/20180223 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 09, 2018 at 01:48:37PM +0200, Tobias Tefke wrote: > In the label skip_full_check the function sanitize_dead_code() > is being called if the return value equals zero. > After that call there is another condition checking > if the return value equals zero. > If this condition evaluates to true, > check_max_stack_depth() is being called. > However, sanitize_dead_code() has no return value. > Therefore the return value of bpf_check() is still the same > and the condition can be removed. > > Signed-off-by: Tobias Tefke > --- > kernel/bpf/verifier.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 9e2bf834f13a..b022d0a85427 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -5935,11 +5935,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) > while (!pop_stack(env, NULL, NULL)); > free_states(env); > > - if (ret == 0) > + if (ret == 0) { > sanitize_dead_code(env); > - > - if (ret == 0) > ret = check_max_stack_depth(env); > + } Technically the patch is correct, but I think it would make the code harder to read. I prefer to keep it as-is.