Add a verifier test that performs an inner array lookup with a constant key that is within the template's max_entries, and then dereferences the lookup result without a NULL check.
The test covers array maps used as inner map templates, where the template's max_entries does not prove that a runtime lookup against a concrete inner map cannot return NULL. The verifier should reject the program because the lookup result must remain PTR_TO_MAP_VALUE_OR_NULL. Signed-off-by: Sun Jian <[email protected]> --- .../selftests/bpf/progs/verifier_map_in_map.c | 44 +++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_map_in_map.c b/tools/testing/selftests/bpf/progs/verifier_map_in_map.c index 16b761e510f0..c650731c6151 100644 --- a/tools/testing/selftests/bpf/progs/verifier_map_in_map.c +++ b/tools/testing/selftests/bpf/progs/verifier_map_in_map.c @@ -18,6 +18,20 @@ struct { }); } map_in_map SEC(".maps"); +struct { + __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS); + __uint(max_entries, 1); + __type(key, int); + __type(value, int); + __array(values, struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 8); + __uint(map_flags, BPF_F_INNER_MAP); + __type(key, int); + __type(value, int); + }); +} map_in_map_inner_array SEC(".maps"); + SEC("socket") __description("map in map access") __success __success_unpriv __retval(0) @@ -139,6 +153,36 @@ __naked void on_the_inner_map_pointer(void) : __clobber_all); } +SEC("socket") +__description("inner array lookup requires null check") +__failure __msg("invalid mem access 'map_value_or_null'") +__failure_unpriv +__naked void inner_array_lookup_requires_null_check(void) +{ + asm volatile (" \ + r1 = 0; \ + *(u32*)(r10 - 4) = r1; \ + r2 = r10; \ + r2 += -4; \ + r1 = %[map_in_map_inner_array] ll; \ + call %[bpf_map_lookup_elem]; \ + if r0 == 0 goto l0_%=; \ + r1 = 6; \ + *(u32*)(r10 - 4) = r1; \ + r2 = r10; \ + r2 += -4; \ + r1 = r0; \ + call %[bpf_map_lookup_elem]; \ + r0 = *(u32*)(r0 + 0); \ + exit; \ +l0_%=: r0 = 0; \ + exit; \ +" : + : __imm(bpf_map_lookup_elem), + __imm_addr(map_in_map_inner_array) + : __clobber_all); +} + SEC("socket") __description("map_ptr is never null") __success -- 2.43.0
