From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www62.your-server.de (www62.your-server.de [213.133.104.62]) (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 58FF1418A39 for ; Mon, 17 Aug 2026 14:10:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.133.104.62 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786975821; cv=none; b=FsTmpenoXuosKjZU2YO60IHVfZY5Vl/46i0VYouyAMhhHG7O734lMYG+DrqkTphL5F+FgnZAGoHVd5kigZm8pmbUiobbfAxHlyEQ/P5uWbst28Xr/mS6MW91mGXYxYjJp1sucL18oWNkdHd0TamASQvsp4VXN2ySTA2UGPBjsg0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786975821; c=relaxed/simple; bh=3dSXIOk6uIKu9ZAyeC4o0SC+xkN8X4IZ801BUnOO914=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=m9h6QVAAXoa4PaFEsRk959lzSpE4uVoF8edOc9gWh7W40KpeuJNsYGeA+dhMZnXJe0EzvyTBAtnlIUKLdKnHlQAixVNO82hRYzuqr1N9s9l3TjcknOAxj5JnD4eGEDpDwAJGTMJACI4Fp+wqQyUsXhGbnbFPkYbKKCQg8WMOnmY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net; spf=pass smtp.mailfrom=iogearbox.net; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b=QT1FgcOS; arc=none smtp.client-ip=213.133.104.62 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=iogearbox.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=iogearbox.net header.i=@iogearbox.net header.b="QT1FgcOS" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=iogearbox.net; s=default2302; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID; bh=EakLggF10eTw8zn+qxxABs/Xl9jQ3q8SHP2uVcWTG7Y=; b=QT1FgcOSI8WoSw+FInRs+XjxNh NCIa6ARScyjtcDeZDnTKdXhunKRZi1e69vgVztGlJ+9Ql9madF7Epbh2V7PST5UsWKKn0clJXQrv3 lyp8mhWszRdSCGQc+sU0uLeAqN19Klig4c5m/NkgSg/CMzn0Y5R8VPzzG+BBT/Tqg9w3ngHbcnSE4 EpA9PFbebTtoSLmqJAF+tO1PQ9pbXoDPaee9yKN5f/btXFr5BkVu6E4kJLs9jkoJFb9ffXe+ls0WL zixkXZ8Xb52I/hUuW/6qG+nzyhzryK7s+yzjCE+TyXGE96dlfxd4j0qp8q9ex5nisZP2eg+h1NF6s hZ4E4xbQ==; Received: from localhost ([127.0.0.1]) by www62.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96.2) (envelope-from ) id 1wvy2b-000MLJ-1a; Mon, 17 Aug 2026 16:10:17 +0200 From: Daniel Borkmann To: eddyz87@gmail.com Cc: memxor@gmail.com, bpf@vger.kernel.org Subject: [PATCH bpf-next v3 3/3] selftests/bpf: Add tests for a store on a fault prone qdisc pointer Date: Mon, 17 Aug 2026 16:10:15 +0200 Message-ID: <20260817141015.878071-3-daniel@iogearbox.net> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260817141015.878071-1-daniel@iogearbox.net> References: <20260817141015.878071-1-daniel@iogearbox.net> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Virus-Scanned: Clear (ClamAV 1.4.3/28095/Mon Aug 17 08:23:59 2026) Cover the store which used to be left as a plain BPF_STX without an exception table entry: 1: R1=trusted_ptr_Qdisc() ; struct Qdisc *next = sch->next_sched; 1: (79) r1 = *(u64 *)(r1 +216) ; R1=ptr_Qdisc() ; next->limit = 1000; 3: (63) *(u32 *)(r1 +20) = r2 ; R1=ptr_Qdisc() R2=1000 Assert that it is rejected now. # LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t ns_bpf_qdisc [...] #257/1 ns_bpf_qdisc/fifo:OK #257/2 ns_bpf_qdisc/fq:OK #257/3 ns_bpf_qdisc/attach to mq:OK #257/4 ns_bpf_qdisc/attach to non root:OK #257/5 ns_bpf_qdisc/incompl_ops:OK #257/6 ns_bpf_qdisc/invalid_dynptr:OK #257/7 ns_bpf_qdisc/invalid_dynptr_cross_frame:OK #257/8 ns_bpf_qdisc/invalid_dynptr_slice:OK #257/9 ns_bpf_qdisc/untrusted_write:OK #257/10 ns_bpf_qdisc/dynptr_use_after_invalidate_clone:OK #257 ns_bpf_qdisc:OK Summary: 1/10 PASSED, 0 SKIPPED, 0/0 FAILED Signed-off-by: Daniel Borkmann --- v2->v3: - new patch .../selftests/bpf/prog_tests/bpf_qdisc.c | 2 + .../progs/bpf_qdisc_fail__untrusted_write.c | 65 +++++++++++++++++++ 2 files changed, 67 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_fail__untrusted_write.c diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c index 77f1c0550c9b..6dbd1487343c 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c @@ -11,6 +11,7 @@ #include "bpf_qdisc_fail__invalid_dynptr.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_slice.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_cross_frame.skel.h" +#include "bpf_qdisc_fail__untrusted_write.skel.h" #include "bpf_qdisc_dynptr_use_after_invalidate_clone.skel.h" #define LO_IFINDEX 1 @@ -230,6 +231,7 @@ void test_ns_bpf_qdisc(void) RUN_TESTS(bpf_qdisc_fail__invalid_dynptr); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_cross_frame); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_slice); + RUN_TESTS(bpf_qdisc_fail__untrusted_write); RUN_TESTS(bpf_qdisc_dynptr_use_after_invalidate_clone); } diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__untrusted_write.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__untrusted_write.c new file mode 100644 index 000000000000..688c2a049ae3 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__untrusted_write.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +SEC("struct_ops") +__failure __msg("only read is supported") +int BPF_PROG(untrusted_write, struct sk_buff *skb, struct Qdisc *sch, + struct bpf_sk_buff_ptr *to_free) +{ + struct Qdisc *next = sch->next_sched; + + /* + * sch is trusted, but the walk of next_sched yields a plain + * PTR_TO_BTF_ID which may fault on a dereference. A store through + * it does not get an exception table entry, there is no probed + * store to rewrite it into, hence it has to be rejected before + * bpf_qdisc_btf_struct_access() gets to allow the write to limit. + */ + next->limit = 1000; + + bpf_qdisc_skb_drop(skb, to_free); + return NET_XMIT_DROP; +} + +SEC("struct_ops") +__auxiliary +struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch) +{ + return NULL; +} + +SEC("struct_ops") +__auxiliary +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + return 0; +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch) +{ +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void *)untrusted_write, + .dequeue = (void *)bpf_qdisc_test_dequeue, + .init = (void *)bpf_qdisc_test_init, + .reset = (void *)bpf_qdisc_test_reset, + .destroy = (void *)bpf_qdisc_test_destroy, + .id = "bpf_qdisc_test", +}; -- 2.43.0