From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Florent Revest <revest@chromium.org>
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 v2 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type
Date: Fri, 26 Mar 2021 15:23:39 -0700 [thread overview]
Message-ID: <CAEf4BzZEgHyodDqj7exrEo+eBOzHEnsvkc003vxq3dcRVZXE2A@mail.gmail.com> (raw)
In-Reply-To: <20210324022211.1718762-3-revest@chromium.org>
On Tue, Mar 23, 2021 at 7:23 PM Florent Revest <revest@chromium.org> wrote:
>
> This type provides the guarantee that an argument is going to be a const
> pointer to somewhere in a read-only map value. It also checks that this
> pointer is followed by a zero character before the end of the map value.
>
> Signed-off-by: Florent Revest <revest@chromium.org>
> ---
> include/linux/bpf.h | 1 +
> kernel/bpf/verifier.c | 38 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 39 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index a25730eaa148..7b5319d75b3e 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -308,6 +308,7 @@ enum bpf_arg_type {
> ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */
> ARG_PTR_TO_FUNC, /* pointer to a bpf program function */
> ARG_PTR_TO_STACK_OR_NULL, /* pointer to stack or NULL */
> + ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */
> __BPF_ARG_TYPE_MAX,
> };
>
[...]
> +
> + map_off = reg->off + reg->var_off.value;
> + err = map->ops->map_direct_value_addr(map, &map_addr, map_off);
> + if (err)
> + return err;
> +
> + str_ptr = (char *)(long)(map_addr);
> + if (!strnchr(str_ptr + map_off,
> + map->value_size - reg->off - map_off, 0))
you are double subtracting reg->off here. isn't map->value_size -
map_off what you want?
> + verbose(env, "string is not zero-terminated\n");
I'd prefer `return -EINVAL;`, but at least set err, otherwise what's the point?
> }
>
> return err;
> --
> 2.31.0.291.g576ba9dcdaf-goog
>
next prev parent reply other threads:[~2021-03-26 22:24 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 2:22 [PATCH bpf-next v2 0/6] Add a snprintf eBPF helper Florent Revest
2021-03-24 2:22 ` [PATCH bpf-next v2 1/6] bpf: Factorize bpf_trace_printk and bpf_seq_printf Florent Revest
2021-03-26 21:53 ` Andrii Nakryiko
2021-03-26 22:51 ` Andrii Nakryiko
2021-04-06 15:35 ` Florent Revest
2021-04-07 21:53 ` Andrii Nakryiko
2021-04-08 22:52 ` Florent Revest
2021-03-24 2:22 ` [PATCH bpf-next v2 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Florent Revest
2021-03-26 22:23 ` Andrii Nakryiko [this message]
2021-04-06 15:38 ` Florent Revest
2021-03-24 2:22 ` [PATCH bpf-next v2 3/6] bpf: Add a bpf_snprintf helper Florent Revest
2021-03-26 22:55 ` Andrii Nakryiko
2021-04-06 16:06 ` Florent Revest
2021-04-07 22:03 ` Andrii Nakryiko
2021-04-08 22:43 ` Florent Revest
2021-03-24 2:22 ` [PATCH bpf-next v2 4/6] libbpf: Initialize the bpf_seq_printf parameters array field by field Florent Revest
2021-03-26 23:01 ` Andrii Nakryiko
2021-04-06 15:42 ` Florent Revest
2021-03-24 2:22 ` [PATCH bpf-next v2 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-03-26 23:02 ` Andrii Nakryiko
2021-03-24 2:22 ` [PATCH bpf-next v2 6/6] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-03-26 23:05 ` Andrii Nakryiko
2021-04-06 15:40 ` Florent Revest
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