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Tue, 09 Jun 2026 15:01:52 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@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: Tue, 09 Jun 2026 15:01:51 -0700 Message-Id: Cc: , , , , Subject: Re: [BUG] bpf: Tracing progs on the stack save subtree can result in OOM From: "Alexei Starovoitov" To: "Mahnur A" , X-Mailer: aerc References: In-Reply-To: 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.