From: Alexei Starovoitov <ast@xxxxxxxxxx>
commit 31e95b61e172144bb2b626a291db1bdc0769275b upstream.
mostly revert the previous workaround and make
'dubious pointer arithmetic' test useful again.
Use (ptr - ptr) << const instead of ptr << const to generate large scalar.
The rest stays as before commit 2b36047e7889.
Fixes: 2b36047e7889 ("selftests/bpf: fix test_align")
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
[fllinden@xxxxxxxxxx: adjust for 4.14 (no liveness of regs in output)]
Signed-off-by: Frank van der Linden <fllinden@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/bpf/test_align.c | 30 +++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)
--- a/tools/testing/selftests/bpf/test_align.c
+++ b/tools/testing/selftests/bpf/test_align.c
@@ -446,11 +446,9 @@ static struct bpf_align_test tests[] = {
.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),
+ /* (ptr - ptr) << 2 */
+ BPF_MOV64_REG(BPF_REG_5, BPF_REG_3),
+ BPF_ALU64_REG(BPF_SUB, 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)
@@ -473,8 +471,26 @@ static struct bpf_align_test tests[] = {
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = REJECT,
.matches = {
- {4, "R5=pkt(id=0,off=0,r=0,imm=0)"},
- /* R5 bitwise operator &= on pointer prohibited */
+ {4, "R5=pkt_end(id=0,off=0,imm=0)"},
+ /* (ptr - ptr) << 2 == unknown, (4n) */
+ {6, "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.
+ */
+ {7, "R5=inv(id=0,var_off=(0x2; 0xfffffffffffffffc))"},
+ /* Checked s>=0 */
+ {9, "R5=inv(id=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ /* packet pointer + nonnegative (4n+2) */
+ {11, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ {13, "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.
+ */
+ {15, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
}
},
{
