From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 053904E4C27; Thu, 17 Sep 2026 15:35:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659359; cv=none; b=qcn4ETZcU45g5Ly0b25KjB030X20jlUatdrv90fV3jlHbCTZjreawEAEYgfizzEh9zIgjMiwmiplhuNdYLDEaTwXx+0ZeB9xF40pVMJ8TI3Gh46axp0LrJsx3tCHMfK9uusnB9W0kwCBctVNhAJJV5cU1gpAtJb2pQ0c6S2WMng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659359; c=relaxed/simple; bh=qBirKQeUh31rM5hYz7NLEmEJq3Vhz+uSFu25m5Y7v0A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Am0xMSWzPZawlt3kgkY5u1jNn3B3SPQ2l2V1YK5thlbCHE4EaElSRIj8mtGcFFwBxQkm9s3FgE3jImlM35XZ/5pDrCRC5vgIcmavKTFQfipEYqSDzcS+lYZxVzpYX8oiNqKbwh30WPhAHKtJnw3T4KBu/54axll1WeWB1z0esHY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZwCWComG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ZwCWComG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3E591F00899; Thu, 17 Sep 2026 15:35:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789659350; bh=mfUwptuYU9DbkZrMIIC26hHud9xh+2IwfcbddpjjvY0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ZwCWComGQFXNh6fz3FF/TpmTOR6T+uWUNDOgIsQfBisKMVdl/2Og89MN2v9ctNHHb VuA+g7T41aSRyrTk6ygTAh3NAzEKIHdNqYrhuWNDIuj/oXkJEhLIM/39p99QEAFaRw 4Rc1cK5UXR0S2tIGJuK/EXVm+z2GqsDisIrmJLvQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jiayuan Chen , Ihor Solodrai , Alexei Starovoitov , Sasha Levin Subject: [PATCH 7.2 227/733] bpf: Fix NULL-ptr-deref when showing a void BTF type Date: Thu, 17 Sep 2026 16:08:55 +0100 Message-ID: <20260917151356.875522711@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen [ Upstream commit 4ea508b9ebd78bce7f212166d2e2cba66b875f08 ] btf_modifier_show() resolves the modifier and then calls btf_type_ops(t)->show() unconditionally. For the void type (type_id 0, BTF_KIND_UNKN) kind_ops[] has no entry, so ->show is NULL. A "const void" (a modifier resolving to void) cannot be a map key or value - map_check_btf() rejects it because void has no size - so the map dump path does not reach it. But bpf_snprintf_btf() takes a type_id straight from the BPF program, and passing such a "const void" from the vmlinux BTF NULL-derefs: KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] RIP: 0010:btf_modifier_show (kernel/bpf/btf.c:2914) Call Trace: btf_type_show (kernel/bpf/btf.c:8251) btf_type_snprintf_show (kernel/bpf/btf.c:8321) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Fall back to btf_df_show() when the resolved type has no show op; it emits the "" placeholder already used for kinds like FWD and FUNC. bpf_snprintf_btf() then returns the length as usual. Fixes: c4d0bfb45068 ("bpf: Add bpf_snprintf_btf helper") Signed-off-by: Jiayuan Chen Acked-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260901104924.346187-3-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/btf.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 608be952717d4..f64eb43cb1f04 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -2912,7 +2912,14 @@ static void btf_modifier_show(const struct btf *btf, else t = btf_type_skip_modifiers(btf, type_id, NULL); - btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show); + /* + * A modifier can resolve to void, which has no show op; print a + * placeholder rather than dereferencing NULL. + */ + if (!btf_type_ops(t)) + btf_df_show(btf, t, type_id, data, bits_offset, show); + else + btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show); } static void btf_var_show(const struct btf *btf, const struct btf_type *t, -- 2.53.0