From: Eduard Zingerman <eddyz87@gmail.com>
To: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
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>,
Shuah Khan <shuah@kernel.org>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH bpf-next 1/2] bpf: Preserve pointer spill metadata during half-slot cleanup
Date: Mon, 15 Jun 2026 10:19:00 -0700 [thread overview]
Message-ID: <56e68303368c8057227e6f35f839bf6426db9ede.camel@gmail.com> (raw)
In-Reply-To: <20260615-f01-06-half-slot-pointer-spill-v1-1-47f1c18a8965@mails.tsinghua.edu.cn>
On Mon, 2026-06-15 at 16:09 +0800, Nuoqi Gui wrote:
> __clean_func_state() cleans dead stack slots in 4-byte halves. When the
> high half of a STACK_SPILL slot is dead and the low half remains live,
> cleanup converts the live low half to STACK_MISC or STACK_ZERO and clears
> the saved spilled_ptr metadata.
>
> That conversion is safe only for scalar spills. For a pointer spill, this
> metadata clear lets a later 32-bit fill from the still-live half avoid the
> normal non-scalar register-fill check and be treated as an ordinary scalar
> stack read.
>
> Leave non-scalar spill slots intact in this half-live shape. This is
> conservative for pruning and preserves the existing
> check_stack_read_fixed_off() rejection path for partial fills from pointer
> spills.
>
> Fixes: 2cb27158adb3 ("bpf: poison dead stack slots")
> Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
> ---
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
[...]
next prev parent reply other threads:[~2026-06-15 17:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-15 8:09 [PATCH bpf-next 0/2] " Nuoqi Gui
2026-06-15 8:09 ` [PATCH bpf-next 1/2] " Nuoqi Gui
2026-06-15 8:48 ` bot+bpf-ci
2026-06-15 9:17 ` Nuoqi Gui
2026-06-15 17:19 ` Eduard Zingerman [this message]
2026-06-15 8:09 ` [PATCH bpf-next 2/2] selftests/bpf: Cover half-slot cleanup of pointer spills Nuoqi Gui
2026-06-15 17:19 ` Eduard Zingerman
2026-06-17 15:20 ` [PATCH bpf-next v2 0/2] bpf: Preserve pointer spill metadata during half-slot cleanup Nuoqi Gui
2026-06-17 15:20 ` [PATCH bpf-next v2 1/2] " Nuoqi Gui
2026-06-22 21:10 ` patchwork-bot+netdevbpf
2026-06-17 15:20 ` [PATCH bpf-next v2 2/2] selftests/bpf: Cover half-slot cleanup of pointer spills Nuoqi Gui
2026-06-17 16:02 ` bot+bpf-ci
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