From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Jay Wang" <wanjay@amazon.com>, <bpf@vger.kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>
Cc: "Ihor Solodrai" <ihor.solodrai@linux.dev>,
"Alan Maguire" <almagui@kernel.org>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Yonghong Song" <yonghong.song@linux.dev>,
"Jiri Olsa" <jolsa@kernel.org>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Masami Hiramatsu" <mhiramat@kernel.org>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
<linux-trace-kernel@vger.kernel.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Nicolas Schier" <nsc@kernel.org>, <linux-kbuild@vger.kernel.org>,
"Arnd Bergmann" <arnd@arndb.de>, <linux-arch@vger.kernel.org>,
<x86@kernel.org>, <linux-doc@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
"Hazem Mohamed Abuelfotoh" <abuehaze@amazon.com>,
"Bjoern Doebel" <doebel@amazon.de>,
"Martin Pohlack" <mpohlack@amazon.de>,
<jay.wang.upstream@gmail.com>
Subject: Re: [PATCH bpf-next 03/13] bpf: check CAP_SYS_ADMIN before looking up bpffs delegation names
Date: Sat, 31 Oct 2026 17:03:04 +0000 [thread overview]
Message-ID: <DMJ6PAVGV9ND.29T5161F064JL@gmail.com> (raw)
In-Reply-To: <20261031130959.23472-4-wanjay@amazon.com>
On Sat, Oct 31, 2026 at 06:09 AM Jay Wang <wanjay@amazon.com> wrote:
> That is free today because the vmlinux BTF is parsed at boot. Once it
> is parsed on first use (CONFIG_DEBUG_INFO_BTF_LAZY, later in this
> series), it would let any user make the kernel parse it and keep it
> parsed until reboot, which is what the option is meant to avoid on
> systems that do not use BTF.
Any user can do that without this mount.
/sys/kernel/btf/vmlinux is 0444. With patch 9 one read() decompresses
5.5 MB into vmalloc_user() memory that is never freed.
The parse is the other 2 MB.
After the first use the kernel has what every BTF=y kernel has today.
There is nothing to guard.
> Check the capability first. An unprivileged caller could only ever set
> an empty mask; such a no-op delegate option, and a malformed value,
> now fail with EPERM as well instead of being accepted or failing with
> EINVAL. Privileged callers are not affected.
That changes what user space sees, with or without the option.
Drop this patch.
next prev parent reply other threads:[~2026-10-31 17:03 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-31 13:09 [PATCH bpf-next 00/13] bpf: keep the vmlinux BTF compressed until first use (CONFIG_DEBUG_INFO_BTF_LAZY) to save ~6 MB memory Jay Wang
2026-10-31 13:09 ` [PATCH bpf-next 01/13] bpf: match program context types by name without vmlinux BTF Jay Wang
2026-10-31 13:43 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 02/13] bpf: fetch the vmlinux BTF where kernel types enter a program Jay Wang
2026-10-31 13:42 ` sashiko-bot
2026-10-31 13:55 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 03/13] bpf: check CAP_SYS_ADMIN before looking up bpffs delegation names Jay Wang
2026-10-31 13:43 ` bot+bpf-ci
2026-10-31 17:03 ` Alexei Starovoitov [this message]
2026-10-31 13:09 ` [PATCH bpf-next 04/13] bpf: move bpf_get_btf_vmlinux() to btf.c Jay Wang
2026-10-31 13:43 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 05/13] bpf: let btf_parse_module() adopt the caller's copy of the module BTF Jay Wang
2026-10-31 13:09 ` [PATCH bpf-next 06/13] bpf: look up the struct_ops common value type in the given BTF Jay Wang
2026-10-31 13:09 ` [PATCH bpf-next 07/13] bpf: parse the vmlinux BTF before taking cand_cache_mutex Jay Wang
2026-10-31 13:43 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 08/13] tracing: parse the vmlinux BTF when BTF-typed output is enabled Jay Wang
2026-10-31 13:37 ` sashiko-bot
2026-10-31 13:43 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 09/13] bpf: keep the vmlinux BTF zstd-compressed in the kernel image Jay Wang
2026-10-31 13:33 ` sashiko-bot
2026-10-31 13:55 ` bot+bpf-ci
2026-10-31 13:09 ` [PATCH bpf-next 10/13] bpf: defer kfunc and struct_ops registrations until first BTF use Jay Wang
2026-10-31 13:38 ` sashiko-bot
2026-10-31 13:55 ` bot+bpf-ci
2026-10-31 17:07 ` Alexei Starovoitov
2026-10-31 13:09 ` [PATCH bpf-next 11/13] bpf: keep module BTF until the vmlinux BTF is parsed Jay Wang
2026-10-31 13:37 ` sashiko-bot
2026-10-31 13:55 ` bot+bpf-ci
2026-10-31 17:10 ` Alexei Starovoitov
2026-10-31 13:09 ` [PATCH bpf-next 12/13] selftests/bpf: keep ksyms and linked_vars working without __start_BTF Jay Wang
2026-10-31 13:09 ` [PATCH bpf-next 13/13] Documentation/bpf: describe CONFIG_DEBUG_INFO_BTF_LAZY Jay Wang
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