ubuntu_bpf/test_verifier failed on B-4.15 (bounds check after 32-bit right shift with 64-bit input FAIL)

[Po-Hsu Lin]

This is not a regression, we don't test ubuntu_bpf on KVM kernels until we have openstack added recently.

Test failed with:
#435/u bounds check after 32-bit right shift with 64-bit input FAIL
Unexpected error message!
0: (7a) *(u64 *)(r10 -8) = 0
1: (bf) r2 = r10
2: (07) r2 += -8
3: (18) r1 = 0x0
5: (85) call bpf_map_lookup_elem#1
6: (15) if r0 == 0x0 goto pc+6
 R0=map_value(id=0,off=0,ks=8,vs=8,imm=0) R10=fp0
7: (b7) r1 = 2
8: (67) r1 <<= 31
9: (74) (u32) r1 >>= (u32) 31
10: (14) (u32) r1 -= (u32) 2
11: (0f) r0 += r1
math between map_value pointer and 4294967294 is not allowed
#435/p bounds check after 32-bit right shift with 64-bit input FAIL
Unexpected error message!
0: (7a) *(u64 *)(r10 -8) = 0
1: (bf) r2 = r10
2: (07) r2 += -8
3: (18) r1 = 0xffff9fe6065f4c00
5: (85) call bpf_map_lookup_elem#1
6: (15) if r0 == 0x0 goto pc+6
 R0=map_value(id=0,off=0,ks=8,vs=8,imm=0) R10=fp0
7: (b7) r1 = 2
8: (67) r1 <<= 31
9: (74) (u32) r1 >>= (u32) 31
10: (14) (u32) r1 -= (u32) 2
11: (0f) r0 += r1
math between map_value pointer and 4294967294 is not allowed

[Po-Hsu Lin (cypressyew)]

This issue exist in all bionic kernels:
  * bionic/linux-aws/4.15.0-1147.159
  * bionic/linux-aws-fips/4.15.0-2083.89
  * bionic/linux-azure-4.15/4.15.0-1158.173
  * bionic/linux-azure-fips/4.15.0-2067.73
  * bionic/linux-gcp-4.15/4.15.0-1142.158
  * bionic/linux-gcp-fips/4.15.0-2051.56
  * bionic/linux-oracle/4.15.0-1109.120