From: Florent Revest <revest@chromium.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
KP Singh <kpsingh@kernel.org>,
Brendan Jackman <jackmanb@chromium.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next 1/5] bpf: Add a ARG_PTR_TO_CONST_STR argument type
Date: Wed, 17 Mar 2021 11:32:40 +0100 [thread overview]
Message-ID: <CABRcYmJSPsW9QRJywH6dLB2mb4aqZPnR9QnWsWhXQ3NGF9OWLQ@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzbiK8vTO_-rgwr43+auTsSfNuTc_zLyR9qH9Dz4NLWsXA@mail.gmail.com>
On Wed, Mar 17, 2021 at 2:02 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
> On Tue, Mar 16, 2021 at 5:46 PM Florent Revest <revest@chromium.org> wrote:
> > On Wed, Mar 17, 2021 at 1:35 AM Andrii Nakryiko
> > <andrii.nakryiko@gmail.com> wrote:
> > > On Tue, Mar 16, 2021 at 4:58 PM Florent Revest <revest@chromium.org> wrote:
> > > > On Tue, Mar 16, 2021 at 2:03 AM Andrii Nakryiko
> > > > <andrii.nakryiko@gmail.com> wrote:
> > > > > On Wed, Mar 10, 2021 at 2:02 PM Florent Revest <revest@chromium.org> wrote:
> > > > > > + } else if (arg_type == ARG_PTR_TO_CONST_STR) {
> > > > > > + struct bpf_map *map = reg->map_ptr;
> > > > > > + int map_off, i;
> > > > > > + u64 map_addr;
> > > > > > + char *map_ptr;
> > > > > > +
> > > > > > + if (!map || !bpf_map_is_rdonly(map)) {
> > > > > > + verbose(env, "R%d does not point to a readonly map'\n", regno);
> > > > > > + return -EACCES;
> > > > > > + }
> > > > > > +
> > > > > > + if (!tnum_is_const(reg->var_off)) {
> > > > > > + verbose(env, "R%d is not a constant address'\n", regno);
> > > > > > + return -EACCES;
> > > > > > + }
> > > > > > +
> > > > > > + if (!map->ops->map_direct_value_addr) {
> > > > > > + verbose(env, "no direct value access support for this map type\n");
> > > > > > + return -EACCES;
> > > > > > + }
> > > > > > +
> > > > > > + err = check_helper_mem_access(env, regno,
> > > > > > + map->value_size - reg->off,
> > > > > > + false, meta);
> > > > >
> > > > > you expect reg to be PTR_TO_MAP_VALUE, so probably better to directly
> > > > > use check_map_access(). And double-check that register is of expected
> > > > > type. just the presence of ref->map_ptr might not be sufficient?
> > > >
> > > > Sorry, just making sure I understand your comment correctly, are you
> > > > suggesting that we:
> > > > 1- skip the check_map_access_type() currently done by
> > > > check_helper_mem_access()? or did you implicitly mean that we should
> > > > call it as well next to check_map_access() ?
> > >
> > > check_helper_mem_access() will call check_map_access() for
> > > PTR_TO_MAP_VALUE and we expect only PTR_TO_MAP_VALUE, right? So why go
> > > through check_helper_mem_access() if we know we need
> > > check_map_access()? Less indirection, more explicit. So I meant
> > > "replace check_helper_mem_access() with check_map_access()".
> >
> > Mhh I suspect there's still a misunderstanding, these function names
> > are really confusing ahah.
> > What about check_map_access*_type*. which is also called by
> > check_helper_mem_access (before check_map_access):
> > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/kernel/bpf/verifier.c#n4329
> >
> > Your message sounds like we should skip it so I was asking if that's
> > what you also implicitly meant or if you missed it?
>
> ah, you meant READ/WRITE access? ok, let's keep
> check_helper_mem_access() then, never mind me
Ah cool, then we are on the same page :)
next prev parent reply other threads:[~2021-03-17 10:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 22:02 [PATCH bpf-next 0/5] Add a snprintf eBPF helper Florent Revest
2021-03-10 22:02 ` [PATCH bpf-next 1/5] bpf: Add a ARG_PTR_TO_CONST_STR argument type Florent Revest
2021-03-11 0:04 ` kernel test robot
2021-03-11 1:00 ` kernel test robot
2021-03-16 1:03 ` Andrii Nakryiko
2021-03-16 23:58 ` Florent Revest
2021-03-17 0:35 ` Andrii Nakryiko
2021-03-17 0:45 ` Florent Revest
2021-03-17 1:02 ` Andrii Nakryiko
2021-03-17 10:32 ` Florent Revest [this message]
2021-03-10 22:02 ` [PATCH bpf-next 2/5] bpf: Add a bpf_snprintf helper Florent Revest
2021-03-11 0:14 ` kernel test robot
2021-03-11 3:12 ` kernel test robot
2021-03-11 3:12 ` [RFC PATCH] bpf: check_bpf_snprintf_call() can be static kernel test robot
2021-03-16 1:25 ` [PATCH bpf-next 2/5] bpf: Add a bpf_snprintf helper Andrii Nakryiko
2021-03-16 13:18 ` Florent Revest
2021-03-23 3:21 ` Alexei Starovoitov
2021-03-23 14:04 ` Florent Revest
2021-03-10 22:02 ` [PATCH bpf-next 3/5] libbpf: Initialize the bpf_seq_printf parameters array field by field Florent Revest
2021-03-16 4:36 ` Andrii Nakryiko
2021-03-16 4:41 ` Andrii Nakryiko
2021-03-16 22:43 ` Florent Revest
2021-03-16 23:06 ` Andrii Nakryiko
2021-03-10 22:02 ` [PATCH bpf-next 4/5] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-03-16 4:39 ` Andrii Nakryiko
2021-03-10 22:02 ` [PATCH bpf-next 5/5] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-03-16 4:49 ` Andrii Nakryiko
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