netdev - [PATCH bpf-next v3 2/6] selftests/bpf: Test tracking spilled unbounded scalars

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Date: Sat, 27 Jan 2024 19:52:33 +0200
From: Maxim Mikityanskiy <maxtram95@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Shung-Hsi Yu <shung-hsi.yu@...e.com>
Cc: John Fastabend <john.fastabend@...il.com>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Mykola Lysenko <mykolal@...com>,
	Shuah Khan <shuah@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	netdev@...r.kernel.org,
	Maxim Mikityanskiy <maxim@...valent.com>
Subject: [PATCH bpf-next v3 2/6] selftests/bpf: Test tracking spilled unbounded scalars

From: Maxim Mikityanskiy <maxim@...valent.com>

The previous commit added tracking for unbounded scalars on spill. Add
the test case to check the new functionality.

Signed-off-by: Maxim Mikityanskiy <maxim@...valent.com>
Acked-by: Eduard Zingerman <eddyz87@...il.com>
---
 .../selftests/bpf/progs/verifier_spill_fill.c | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index 317806451762..f9803005e1c0 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -940,4 +940,31 @@ l0_%=:	r0 = 0;						\
 	: __clobber_all);
 }
 
+SEC("xdp")
+__description("spill unbounded reg, then range check src")
+__success __retval(0)
+__naked void spill_unbounded(void)
+{
+	asm volatile ("					\
+	/* Produce an unbounded scalar. */		\
+	call %[bpf_get_prandom_u32];			\
+	/* Spill r0 to stack. */			\
+	*(u64*)(r10 - 8) = r0;				\
+	/* Boundary check on r0. */			\
+	if r0 > 16 goto l0_%=;				\
+	/* Fill r0 from stack. */			\
+	r0 = *(u64*)(r10 - 8);				\
+	/* Boundary check on r0 with predetermined result. */\
+	if r0 <= 16 goto l0_%=;				\
+	/* Dead branch: the verifier should prune it. Do an invalid memory\
+	 * access if the verifier follows it.		\
+	 */						\
+	r0 = *(u64*)(r9 + 0);				\
+l0_%=:	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.43.0