From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Jiale Yao" <yaojiale02@163.com>, "KP Singh" <kpsingh@kernel.org>,
"Matt Bobrowski" <matt@bobrowski.net>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Song Liu" <song@kernel.org>,
"Yonghong Song" <yonghong.song@linux.dev>,
"Jiri Olsa" <jolsa@kernel.org>,
"Emil Tsalapatis" <emil@etsalapatis.com>,
"Ihor Solodrai" <ihor.solodrai@linux.dev>,
"Roberto Sassu" <roberto.sassu@huawei.com>, <bpf@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Cc: <stable@vger.kernel.org>
Subject: Re: [PATCH] bpf: Initialize IMA hash helper output buffers
Date: Mon, 28 Sep 2026 07:38:57 +0000 [thread overview]
Message-ID: <DLQS1EUNZG5T.1ZCONM8DQM45@gmail.com> (raw)
In-Reply-To: <20260927121400.1188165-1-yaojiale02@163.com>
On Sun, Sep 27, 2026 at 08:14 PM Jiale Yao <yaojiale02@163.com> wrote:
> The output arguments of bpf_ima_inode_hash() and bpf_ima_file_hash()
> are marked as ARG_PTR_TO_UNINIT_MEM, so the verifier considers the full
> range initialized after either helper returns. The IMA hash functions,
> however, leave the buffer unchanged on error and only copy the digest
> length on success. A BPF program can therefore read stale data from
> the untouched portion of the buffer.
That's not a bug.
These helpers are available to LSM progs only and LSM progs
require CAP_PERFMON to load.
With CAP_PERFMON the verifier allows reading uninitialized stack
with or without the helper call.
Since commit 5da4a9f26fca ("bpf: Preserve stack initialization for
generic output buffers") MEM_UNINIT helpers don't have to write
the whole buffer.
pw-bot: cr
next prev parent reply other threads:[~2026-09-28 7:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-27 12:14 [PATCH] bpf: Initialize IMA hash helper output buffers Jiale Yao
2026-09-28 7:38 ` Alexei Starovoitov [this message]
2026-09-28 11:43 ` Matt Bobrowski
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