From: Martin KaFai Lau <kafai@fb.com>

Date: Mon, 1 Nov 2021 23:45:41 -0700

Subject: selftests/bpf: Verifier test on refill from a smaller spill

Patch-mainline: v5.16-rc1

Git-commit: c08455dec5acf4668f5d1eb099f7fedb29f2de5f

References: jsc#PED-1377

This patch adds a verifier test to ensure the verifier can read 8 bytes

from the stack after two 32bit write at fp-4 and fp-8. The test is similar

to the reported case from bcc [0].

  [0] https://github.com/iovisor/bcc/pull/3683

Signed-off-by: Martin KaFai Lau <kafai@fb.com>

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Acked-by: Yonghong Song <yhs@fb.com>

Link: https://lore.kernel.org/bpf/20211102064541.316414-1-kafai@fb.com

Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>

---

 tools/testing/selftests/bpf/verifier/spill_fill.c |   17 +++++++++++++++++

 1 file changed, 17 insertions(+)

--- a/tools/testing/selftests/bpf/verifier/spill_fill.c

+++ b/tools/testing/selftests/bpf/verifier/spill_fill.c

@@ -265,3 +265,20 @@

 	.result = ACCEPT,

 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,

 },

+{

+	"Spill a u32 scalar at fp-4 and then at fp-8",

+	.insns = {

+	/* r4 = 4321 */

+	BPF_MOV32_IMM(BPF_REG_4, 4321),

+	/* *(u32 *)(r10 -4) = r4 */

+	BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -4),

+	/* *(u32 *)(r10 -8) = r4 */

+	BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_4, -8),

+	/* r4 = *(u64 *)(r10 -8) */

+	BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8),

+	BPF_MOV64_IMM(BPF_REG_0, 0),

+	BPF_EXIT_INSN(),

+	},

+	.result = ACCEPT,

+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,

+},