From: Eduard Zingerman <eddyz87@gmail.com>
To: Kumar Kartikeya Dwivedi <memxor@gmail.com>, bpf@vger.kernel.org
Cc: Sashiko <sashiko-bot@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Emil Tsalapatis <emil@etsalapatis.com>,
kkd@meta.com, kernel-team@meta.com
Subject: Re: [PATCH bpf-next v1 01/14] bpf: Correct verifier diagnostic attribution for stack reads
Date: Sat, 15 Aug 2026 23:34:40 -0700 [thread overview]
Message-ID: <b0846b8a8611ae6084a1e0190c21fe93000ade29.camel@gmail.com> (raw)
In-Reply-To: <20260816015746.2632990-2-memxor@gmail.com>
On Sun, 2026-08-16 at 03:57 +0200, Kumar Kartikeya Dwivedi wrote:
...
> @@ -4079,13 +4106,13 @@ static int check_stack_read(struct bpf_verifier_env *env,
> tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
> verbose(env, "variable offset stack pointer cannot be passed into helper function; var_off=%s off=%d size=%d\n",
> tn_buf, off, size);
> - reason = bpf_diag_fmt(env,
> - "The helper would access the stack through variable offset %s plus fixed offset %d and size %d. "
> - "Helper stack memory arguments require a constant stack offset and a precise initialized range.",
> + reason = bpf_diag_fmt(
> + env, "The atomic operation would access the stack through variable offset %s plus fixed offset %d and size %d. "
> + "Atomic stack operations require a constant stack offset and a precise initialized range.",
Relying on value_regno being -1 only for atomic operations is very fragile.
Let's at-least make a comment. Or make the wording neutral,
like "instruction variable offset access ..." (best).
Or check the actual instruction and vary wording.
> tn_buf, off, size);
> bpf_diag_memory(
> - env, env->insn_idx, "variable stack access", reason,
> - "Use a fixed stack offset for helper memory arguments, or copy the needed bytes into a fixed stack slot first.");
> + env, env->insn_idx, "variable-offset atomic stack access", reason,
> + "Use a fixed stack offset for the atomic operation, selecting the target stack slot on separate control-flow paths if necessary.");
> return -EACCES;
> }
> /* Variable offset is prohibited for unprivileged mode for simplicity
next prev parent reply other threads:[~2026-08-16 6:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-16 1:57 [PATCH bpf-next v1 00/14] Follow ups for verifier errors set Kumar Kartikeya Dwivedi
2026-08-16 1:57 ` [PATCH bpf-next v1 01/14] bpf: Correct verifier diagnostic attribution for stack reads Kumar Kartikeya Dwivedi
2026-08-16 6:34 ` Eduard Zingerman [this message]
2026-08-16 1:57 ` [PATCH bpf-next v1 02/14] selftests/bpf: Test verifier stack-read diagnostic attribution Kumar Kartikeya Dwivedi
2026-08-16 2:45 ` bot+bpf-ci
2026-08-16 6:35 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 03/14] bpf: Preserve R0 lineage across helper calls Kumar Kartikeya Dwivedi
2026-08-16 2:30 ` bot+bpf-ci
2026-08-16 6:12 ` Eduard Zingerman
2026-08-16 6:36 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 04/14] bpf: Drop dead spill diagnostic condition Kumar Kartikeya Dwivedi
2026-08-16 6:39 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 05/14] bpf: Use canonical stack argument names in diagnostics Kumar Kartikeya Dwivedi
2026-08-16 6:40 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 06/14] bpf: Correct kfunc argument diagnostics Kumar Kartikeya Dwivedi
2026-08-16 2:45 ` bot+bpf-ci
2026-08-16 6:50 ` Eduard Zingerman
2026-08-16 6:52 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 07/14] selftests/bpf: Test " Kumar Kartikeya Dwivedi
2026-08-16 6:53 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 08/14] bpf: Report non-sleepable kfunc programs accurately Kumar Kartikeya Dwivedi
2026-08-16 2:30 ` bot+bpf-ci
2026-08-16 7:32 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 09/14] selftests/bpf: Test non-sleepable kfunc context Kumar Kartikeya Dwivedi
2026-08-16 2:30 ` bot+bpf-ci
2026-08-16 7:37 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 10/14] bpf: Correct Program Structure diagnostic context Kumar Kartikeya Dwivedi
2026-08-16 2:45 ` bot+bpf-ci
2026-08-16 7:58 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 11/14] bpf: Preserve source attribution without source text Kumar Kartikeya Dwivedi
2026-08-16 8:01 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 12/14] selftests/bpf: Test Program Structure diagnostic context Kumar Kartikeya Dwivedi
2026-08-16 8:06 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 13/14] bpf: Distinguish function references in policy diagnostics Kumar Kartikeya Dwivedi
2026-08-16 8:09 ` Eduard Zingerman
2026-08-16 1:57 ` [PATCH bpf-next v1 14/14] selftests/bpf: Test pseudo-function " Kumar Kartikeya Dwivedi
2026-08-16 2:45 ` bot+bpf-ci
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