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Mon, 20 Apr 2026 08:46:50 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 20 Apr 2026 08:46:49 -0700 Message-Id: Subject: Re: [PATCH bpf-next v10 2/6] bpf: Add bpf_prog_run_array_sleepable() From: "Alexei Starovoitov" To: "Mykyta Yatsenko" , "bpf" , "Alexei Starovoitov" , "Andrii Nakryiko" , "Daniel Borkmann" , "Martin Lau" , "Kernel Team" , "Eduard" , "Kumar Kartikeya Dwivedi" , "Peter Zijlstra" , "Steven Rostedt" Cc: "Mykyta Yatsenko" X-Mailer: aerc References: <20260415-sleepable_tracepoints-v10-0-161f40b33dd7@meta.com> <20260415-sleepable_tracepoints-v10-2-161f40b33dd7@meta.com> <337f2570-acb2-4b31-8c4f-86ba4cbdfe65@gmail.com> In-Reply-To: <337f2570-acb2-4b31-8c4f-86ba4cbdfe65@gmail.com> On Fri Apr 17, 2026 at 10:22 AM PDT, Mykyta Yatsenko wrote: > > > On 4/16/26 3:40 PM, Alexei Starovoitov wrote: >> On Wed, Apr 15, 2026 at 6:41=E2=80=AFPM Alexei Starovoitov >> wrote: >> One more thing.. >> Please go back to my 'do your homework' request from v9 >> and answer the question why it's not safe to do bpf_prog_run >> on dummy prog like this patch does. >> I missed it yesterday and only complained about the waste of cpu cycles. >> It's more than that. >>=20 >> Do not send v11. > > I see that very similar bug was fixed in 7dc211c1159d ("bpf: Fix invalid= =20 > prog->stats access when update_effective_progs fails"), the problem is=20 > the same - NULL field access on the dummy prog. So the approach to just= =20 > allow dummy to run further is fragile, because other NULL fields may be= =20 > accessed. exactly. so far we've hit 'active =3D=3D NULL' and 'stats =3D=3D NULL', and 'stats =3D=3D NULL' had to be workaround-ed like that in that commit. There is also 'aux'. I hope it's not used at run-time, but let's not take c= hances. Filter dummy prog as immediate skip.