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 271C6408028; Wed, 30 Sep 2026 19:06:36 +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=1790795198; cv=none; b=S+tNea+zDla/VJ7stL2E0lh4HivC95rXbXPQmdVN9r57obtVKra3Nq6HshiLtaKH/5+PV57X2JuJG1CGa2bt+byTz0akNF/Q01rmvp8Bh6PIkK5Yu7nZo4lfdQ9RJdwAKQ6JJeydQIRydj9EOaK7k/MmhGdqVULUf+E7KB7sZww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790795198; c=relaxed/simple; bh=BMpVdi1xUiIEIDPjC2VEPWVhGsANzCkyg5phS2cTGtM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TOf2NEjJ+bQHc/Gwxf2ypn7FX+pCQDY8lZKaukdAh9OB5dEyWl0ib8KX6m4Ev53eQNmcxygCQIaImX/gS0pdcKenZkEe9Zl7VD8RVVWNjvOCI3yPT5V/39JaS3s6ZOV9ZYqL60iJZuW+JE3Yidq3CsCqOD4x6izx0kSz/XOK82c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pNhohAVH; 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="pNhohAVH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 562AA1F000FF; Wed, 30 Sep 2026 19:06:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790795196; bh=jMcLavv0YJsvh9A3HACST+/o8YhgJP+gc9tEg0rE1uc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=pNhohAVHDEUVyUyeIIMb1wnrUbhv3OmbeXoaPWFWlHstFuMEOpK8+5X4UaNphPsio StaZecjiZ5gd5qhzvEnNNvpLfA92FMA6ApGTKRGDQv3GZg/3zF+R3AYS/b1BN4CW6f mPURYBBpBOBkV/mA1ynaazhr+iT//cGNtZ+m2lWA= 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 6.6 0478/1193] bpf: Fix NULL-ptr-deref when showing a void BTF type Date: Wed, 30 Sep 2026 17:19:22 +0200 Message-ID: <20260930152444.781802909@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@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 6.6-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 1ace7faa59cfd..f913437e97b22 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -2718,7 +2718,14 @@ 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