From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Yauheni Kaliuta yauheni.kaliuta@redhat.com
commit 6185266c5a853bb0f2a459e3ff594546f277609b upstream.
The verifier test labelled "valid read map access into a read-only array 2" calls the bpf_csum_diff() helper and checks its return value. However, architecture implementations of csum_partial() (which is what the helper uses) differ in whether they fold the return value to 16 bit or not. For example, x86 version has ...
if (unlikely(odd)) { result = from32to16(result); result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); }
... while generic lib/checksum.c does:
result = from32to16(result); if (odd) result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
This makes the helper return different values on different architectures, breaking the test on non-x86. To fix this, add an additional instruction to always mask the return value to 16 bits, and update the expected return value accordingly.
Fixes: fb2abb73e575 ("bpf, selftest: test {rd, wr}only flags and direct value access") Signed-off-by: Yauheni Kaliuta yauheni.kaliuta@redhat.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20210228103017.320240-1-yauheni.kaliuta@redhat.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/bpf/verifier/array_access.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/tools/testing/selftests/bpf/verifier/array_access.c +++ b/tools/testing/selftests/bpf/verifier/array_access.c @@ -250,12 +250,13 @@ BPF_MOV64_IMM(BPF_REG_5, 0), BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_csum_diff), + BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffff), BPF_EXIT_INSN(), }, .prog_type = BPF_PROG_TYPE_SCHED_CLS, .fixup_map_array_ro = { 3 }, .result = ACCEPT, - .retval = -29, + .retval = 65507, }, { "invalid write map access into a read-only array 1",