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From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Florent Revest (Anthropic)" <florent.revest@linux.dev>,
	<bpf@vger.kernel.org>, "Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Andrii Nakryiko" <andrii@kernel.org>
Cc: "Martin KaFai Lau" <martin.lau@linux.dev>,
	"Eduard Zingerman" <eddyz87@gmail.com>,
	"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
	"Song Liu" <song@kernel.org>,
	"Yonghong Song" <yonghong.song@linux.dev>,
	"Jiri Olsa" <jolsa@kernel.org>, "KP Singh" <kpsingh@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Leon Hwang" <leon.hwang@linux.dev>,
	"Junseo Lim" <zirajs7@gmail.com>,
	"Sechang Lim" <rhkrqnwk98@gmail.com>,
	"Puranjay Mohan" <puranjay@kernel.org>,
	"Xu Kuohai" <xukuohai@huaweicloud.com>,
	"Ilya Leoshkevich" <iii@linux.ibm.com>,
	"Hari Bathini" <hbathini@linux.ibm.com>,
	"Christophe Leroy" <chleroy@kernel.org>,
	"Naveen N Rao" <naveen@kernel.org>,
	"Björn Töpel" <bjorn@kernel.org>, "Pu Lehui" <pulehui@huawei.com>,
	"Tiezhu Yang" <yangtiezhu@loongson.cn>,
	"Hengqi Chen" <hengqi.chen@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf v3 2/3] bpf: Skip the progs of trampoline images that are being freed
Date: Fri, 25 Sep 2026 00:35:29 +0000	[thread overview]
Message-ID: <DLNZ5JQGHKP6.3TN7S6R9IFH5C@gmail.com> (raw)
In-Reply-To: <20260924170543.1017048-3-florent.revest@linux.dev>

On Thu Sep 24, 2026 at 5:05 PM UTC, Florent Revest (Anthropic) wrote:
> call sequences, which replaces ip_after_call. Tasks that are still in an
> image that was put skip all of its progs from then on, including the
> ones that are still attached, like they already skipped its fexit
> progs. The call to the original function is left alone, a task that is
> before it in the image still has to run it.

So I slept on it and you were right to argue that skipping fmod_ret
is a bad idea. bpf-ci explains it well.

So let's patch only the progs that are being detached instead of all.
Pretty much what you had in v2, but also explain why list is needed
and why just patching previous tramp is not enough.

Also see CI re: lower limit for x86.

Adjusting BPF_MAX_TRAMP_LINKS for large page sizes is a bigger change.
Ignore it for now.

pw-bot: cr

  parent reply	other threads:[~2026-09-25  0:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-24 17:05 [PATCH bpf v3 0/3] bpf: Fix use-after-free of progs detached from busy trampolines Florent Revest (Anthropic)
2026-09-24 17:05 ` [PATCH bpf v3 1/3] bpf: Wait for an RCU tasks grace period before freeing trampoline progs Florent Revest (Anthropic)
2026-09-24 17:05 ` [PATCH bpf v3 2/3] bpf: Skip the progs of trampoline images that are being freed Florent Revest (Anthropic)
2026-09-24 18:07   ` bot+bpf-ci
2026-09-25  0:35   ` Alexei Starovoitov [this message]
2026-09-24 17:05 ` [PATCH bpf v3 3/3] selftests/bpf: Detach a trampoline prog while a task sleeps before it Florent Revest (Anthropic)
2026-09-24 17:53   ` bot+bpf-ci

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