From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Mahnur A" <s.mahnur.a@gmail.com>, <bpf@vger.kernel.org>
Cc: <ast@kernel.org>, <daniel@iogearbox.net>, <andrii@kernel.org>,
<rostedt@goodmis.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] bpf: Tracing progs on the stack save subtree can result in OOM
Date: Tue, 09 Jun 2026 15:01:51 -0700 [thread overview]
Message-ID: <DJ4UVMEEOUIF.8C5PH54S5HSK@gmail.com> (raw)
In-Reply-To: <CAJ-umGQ9edRUCnaLYTW1F2wbRDhxM7RRra545ZYbM+8++ModaA@mail.gmail.com>
On Tue Jun 9, 2026 at 10:04 AM PDT, Mahnur A wrote:
> Hi,
>
> I hit the following case on the current mainline kernel (7.1-rc7)
>
> BPF tracing programs that allocate something and have a deferred-free for it:
> Attached to any function in the stack save / unwind result in OOM.
>
>
> KASAN, slub_debug etc. all save a stack on every alloc/free.
> An example bpf program updates a map element,
> before lookup and retrieval of the timer object.
> It then calls bpf_timer_init().
> If this happens at every alloc/free event,
> a new timer object gets allocated with every map element update,
> while the previous one is deferred-free (via kfree_rcu).
It's a known design constraint.
A bunch of things in the kernel need call_rcu().
bpf is not immune to such requirements.
prev parent reply other threads:[~2026-06-09 22:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-09 17:04 [BUG] bpf: Tracing progs on the stack save subtree can result in OOM Mahnur A
2026-06-09 22:01 ` Alexei Starovoitov [this message]
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