From: Alexei Starovoitov ast@kernel.org
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@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net [fllinden@amazon.com: adjust for 4.14 (no liveness of regs in output)] Signed-off-by: Frank van der Linden fllinden@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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))"}, } }, {