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Subject[PATCH v3 net-next 09/12] selftests/bpf: add test for bogus operations on pointers
Date
Tests non-add/sub operations (AND, LSH) on pointers decaying them to
unknown scalars.
Also tests that a pkt_ptr add which could potentially overflow is rejected
(find_good_pkt_pointers ignores it and doesn't give us any reg->range).

Signed-off-by: Edward Cree <ecree@solarflare.com>
---
tools/testing/selftests/bpf/test_align.c | 66 +++++++++++++++++++++++++++++++-
1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_align.c b/tools/testing/selftests/bpf/test_align.c
index 5165d8e..dfd96c6 100644
--- a/tools/testing/selftests/bpf/test_align.c
+++ b/tools/testing/selftests/bpf/test_align.c
@@ -441,6 +441,62 @@ static struct bpf_align_test tests[] = {
{23, "R5=pkt(id=2,off=0,r=4,umin_value=14,umax_value=2054,var_off=(0x2; 0xffc))"},
},
},
+ {
+ .descr = "dubious pointer arithmetic",
+ .insns = {
+ PREP_PKT_POINTERS,
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ /* ptr & const => unknown & const */
+ BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_5, 0x40),
+ /* ptr << const => unknown << const */
+ BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
+ BPF_ALU64_IMM(BPF_LSH, BPF_REG_5, 2),
+ /* We have a (4n) value. Let's make a packet offset
+ * out of it. First add 14, to make it a (4n+2)
+ */
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
+ /* Then make sure it's nonnegative */
+ BPF_JMP_IMM(BPF_JSGE, BPF_REG_5, 0, 1),
+ BPF_EXIT_INSN(),
+ /* Add it to packet pointer */
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_2),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_5),
+ /* Check bounds and perform a read */
+ BPF_MOV64_REG(BPF_REG_4, BPF_REG_6),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
+ BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
+ BPF_EXIT_INSN(),
+ BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_6, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .result = REJECT,
+ .matches = {
+ {4, "R5=pkt(id=0,off=0,r=0,imm=0)"},
+ /* ptr & 0x40 == either 0 or 0x40 */
+ {5, "R5=inv(id=0,umax_value=64,var_off=(0x0; 0x40))"},
+ /* ptr << 2 == unknown, (4n) */
+ {7, "R5=inv(id=0,smax_value=9223372036854775804,umax_value=18446744073709551612,var_off=(0x0; 0xfffffffffffffffc))"},
+ /* (4n) + 14 == (4n+2). We blow our bounds, because
+ * the add could overflow.
+ */
+ {8, "R5=inv(id=0,var_off=(0x2; 0xfffffffffffffffc))"},
+ /* Checked s>=0 */
+ {10, "R5=inv(id=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ /* packet pointer + nonnegative (4n+2) */
+ {12, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ {14, "R4=pkt(id=1,off=4,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ /* NET_IP_ALIGN + (4n+2) == (4n), alignment is fine.
+ * We checked the bounds, but it might have been able
+ * to overflow if the packet pointer started in the
+ * upper half of the address space.
+ * So we did not get a 'range' on R6, and the access
+ * attempt will fail.
+ */
+ {16, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ }
+ },
};

static int probe_filter_length(const struct bpf_insn *fp)
@@ -470,10 +526,15 @@ static int do_test_single(struct bpf_align_test *test)
fd_prog = bpf_verify_program(prog_type ? : BPF_PROG_TYPE_SOCKET_FILTER,
prog, prog_len, 1, "GPL", 0,
bpf_vlog, sizeof(bpf_vlog));
- if (fd_prog < 0) {
+ if (fd_prog < 0 && test->result != REJECT) {
printf("Failed to load program.\n");
printf("%s", bpf_vlog);
ret = 1;
+ } else if (fd_prog >= 0 && test->result == REJECT) {
+ printf("Unexpected success to load!\n");
+ printf("%s", bpf_vlog);
+ ret = 1;
+ close(fd_prog);
} else {
ret = 0;
/* We make a local copy so that we can strtok() it */
@@ -506,7 +567,8 @@ static int do_test_single(struct bpf_align_test *test)
break;
}
}
- close(fd_prog);
+ if (fd_prog >= 0)
+ close(fd_prog);
}
return ret;
}
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