From nobody Mon Sep 28 22:32:16 2026 Received: from oss.cyber.gouv.fr (oss.cyber.gouv.fr [51.159.188.251]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2CC0B2D877A; Sun, 16 Aug 2026 20:46:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=51.159.188.251 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786913166; cv=none; b=WFffT2agmFqkrC4E6OciUe8JOHIP7GLGxS04WbhOSb1kAmbwnUmgVbWbFL7FIn6jborIL+gRjdhge3Y/bXGYEfVm0zqKaDo28J2N8YlHLdX2yeuc8EG58TTmUg4vqfXNU8etwEXeuNuz9y5C2vSlltjR/RQJIjeR4Wkav25sL5A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786913166; c=relaxed/simple; bh=+vbmDQjyHdvOJM0g9AkHaKvncDjH+6SOqUc0vnGD0GA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=huHfEgZgGEBIu6a0SgfvSVTeD1QgeuT7EGMW9hmuVLTj8CWk9tBumd7ccR1Q1EwX7OuytrWxPfRZDY80Rv3B+zCBqQpJOn4UYTE/YFSFEPkC9TvxhiqbEyLz4q4kLe60tmxk3CA6rI5dL6Cf6rz2dbfGQD/tWoC9XDtP4LpW+G0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=oss.cyber.gouv.fr; spf=pass smtp.mailfrom=oss.cyber.gouv.fr; dkim=pass (2048-bit key) header.d=oss.cyber.gouv.fr header.i=@oss.cyber.gouv.fr header.b=BkcV2Geh; arc=none smtp.client-ip=51.159.188.251 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=oss.cyber.gouv.fr Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.cyber.gouv.fr Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=oss.cyber.gouv.fr header.i=@oss.cyber.gouv.fr header.b="BkcV2Geh" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=oss.cyber.gouv.fr; s=default; h=Content-Transfer-Encoding:Content-Type: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=Z8PE2QwmRoYXLYZc03fkDtCQdTD7ol+eYcE4/BDCVwU=; b=BkcV2GehtrDP+W/+hdPrpyDbxb dxlvt/Nyi1c8heVonYJPrcU/4E0ruXA1TyA/LwmkJ/RU6uVysZpAeBqj3/3Zoffv+Oo8oFvTFAn2S AxlMSN5Aa6WsNH0vo/u5O4fKBZKWQqlqjHoeROuoVvTlqzowGZUbAwGXKme3NX4MddjRSf6q5zwWB iIX1WXPPzgBEb9Y19xYTEZ7UDsAbqtwEFkez/p5oDH8Ut5mfhBuvcIaKY3TI54ls31mpUcCpdybJl zZ7fFyFn8gfc0dJcUMUer6l1pGR5mztHzN6zO3xTp0NlVoFsSFQjNnVTqobsST3wR6flJBJAewSjf p7pCgERw==; Received: from [151.115.150.205] (port=49152 helo=gepetto..) by pf-012.whm.fr-par.scw.cloud with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1wvhjw-0000000938B-1bOJ; Sun, 16 Aug 2026 22:45:56 +0200 From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= Subject: [PATCH] bpf: reject stack-argument callback subprograms Date: Sun, 16 Aug 2026 20:45:02 +0000 Message-ID: <20260816204501.493914-2-Jeremy.Jean@oss.cyber.gouv.fr> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - pf-012.whm.fr-par.scw.cloud X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - oss.cyber.gouv.fr X-Get-Message-Sender-Via: pf-012.whm.fr-par.scw.cloud: authenticated_id: jeremy.jean@oss.cyber.gouv.fr X-Authenticated-Sender: pf-012.whm.fr-par.scw.cloud: jeremy.jean@oss.cyber.gouv.fr X-Source: X-Source-Args: X-Source-Dir: Helper callbacks enter BPF subprograms through bpf_callback_t, whose runtime ABI supplies five arguments. BTF validation nevertheless permits static callback subprograms to declare more than five arguments when JIT stack arguments are supported. This lets verifier state for a callback use outgoing stack argument slots prepared at the helper call site. The helper does not pass those slots. On x86-64, callback loads of arguments seven and later therefore read the helper native frame instead of the synthetic values checked by the verifier. KASAN reports a slab OOB write. Reject callback subprograms with incoming stack arguments when processing callback calls. Add a verifier regression test using bpf_loop() and a nine-argument callback. Fixes: 0f6bd5e7a804 ("bpf: Support stack arguments for bpf functions") Assisted-by: Codex:gpt-5 Signed-off-by: J=C3=A9r=C3=A9my Jean --- kernel/bpf/verifier.c | 4 +++ .../selftests/bpf/progs/verifier_stack_arg.c | 33 +++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index fdc5fbb1f78c..29aa4911c7f7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9285,6 +9285,10 @@ static int push_callback_call(struct bpf_verifier_en= v *env, struct bpf_insn *ins err =3D btf_check_subprog_call(env, subprog, caller->regs); if (err =3D=3D -EFAULT) return err; + if (bpf_in_stack_arg_cnt(&env->subprog_info[subprog])) { + verbose(env, "callback subprog cannot have stack args\n"); + return -EINVAL; + } =20 /* set_callee_state is used for direct subprog calls, but we are * interested in validating only BPF helpers that can call subprogs as diff --git a/tools/testing/selftests/bpf/progs/verifier_stack_arg.c b/tools= /testing/selftests/bpf/progs/verifier_stack_arg.c index 7e0ce5db28a0..5acc3b63ca84 100644 --- a/tools/testing/selftests/bpf/progs/verifier_stack_arg.c +++ b/tools/testing/selftests/bpf/progs/verifier_stack_arg.c @@ -27,6 +27,13 @@ static int subprog_7args(int a, int b, int c, int d, int= e, int f, int g) return a + b + c + d + e + f + g; } =20 +__noinline __used +static int callback_9args(__u32 index, void *ctx, long a3, long a4, + long a5, long a6, long a7, long a8, long a9) +{ + return a9; +} + __noinline __used static long subprog_deref_arg6(long a, long b, long c, long d, long e, lon= g *f) { @@ -79,6 +86,32 @@ __naked void stack_arg_two_subprogs(void) ); } =20 +SEC("tc") +__description("stack_arg: callback with incoming stack args") +__failure +__msg("callback subprog cannot have stack args") +__naked void stack_arg_callback_many_args(void) +{ + asm volatile ( + "r6 =3D 0;" + "*(u64 *)(r11 - 32) =3D 0;" + "*(u64 *)(r11 - 24) =3D 0;" + "*(u64 *)(r11 - 16) =3D 0;" + "*(u64 *)(r11 - 8) =3D 0;" + "r1 =3D 1;" + "r2 =3D %[callback_9args];" + "r3 =3D 0;" + "r4 =3D 0;" + "call %[bpf_loop];" + "r0 =3D 0;" + "exit;" + : + : __imm_ptr(callback_9args), + __imm(bpf_loop) + : __clobber_all + ); +} + SEC("tc") __description("stack_arg: read from uninitialized stack arg slot") __failure --=20 2.47.3