A test requires the following to happen: * CONST_PTR_TO_MAP value is checked for null * the code in the null branch fails verification Add test cases: * direct global map_ptr comparison to null * lookup inner map, then two checks (the first transforms map_value_or_null into map_ptr) * lookup inner map, spill-fill it, then check for null * use an array of ringbufs to recreate a common coding pattern [1] [1] https://lore.kernel.org/bpf/CAEf4BzZNU0gX_sQ8k8JaLe1e+Veth3Rk=4x7MDhv=hQxvO8EDw@xxxxxxxxxxxxxx/ Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Signed-off-by: Ihor Solodrai <isolodrai@xxxxxxxx> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- .../selftests/bpf/progs/verifier_map_in_map.c | 118 ++++++++++++++++++ 1 file changed, 118 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 7d088ba99ea5..16b761e510f0 100644 --- a/tools/testing/selftests/bpf/progs/verifier_map_in_map.c +++ b/tools/testing/selftests/bpf/progs/verifier_map_in_map.c @@ -139,4 +139,122 @@ __naked void on_the_inner_map_pointer(void) : __clobber_all); } +SEC("socket") +__description("map_ptr is never null") +__success +__naked void map_ptr_is_never_null(void) +{ + asm volatile (" \ + r0 = 0; \ + r1 = %[map_in_map] ll; \ + if r1 != 0 goto l0_%=; \ + r10 = 42; \ +l0_%=: exit; \ +" : + : __imm(bpf_map_lookup_elem), + __imm_addr(map_in_map) + : __clobber_all); +} + +SEC("socket") +__description("map_ptr is never null inner") +__success +__naked void map_ptr_is_never_null_inner(void) +{ + asm volatile (" \ + r1 = 0; \ + *(u32*)(r10 - 4) = r1; \ + r2 = r10; \ + r2 += -4; \ + r1 = %[map_in_map] ll; \ + call %[bpf_map_lookup_elem]; \ + if r0 == 0 goto l0_%=; \ + if r0 != 0 goto l0_%=; \ + r10 = 42; \ +l0_%=: exit; \ +" : + : __imm(bpf_map_lookup_elem), + __imm_addr(map_in_map) + : __clobber_all); +} + +SEC("socket") +__description("map_ptr is never null inner spill fill") +__success +__naked void map_ptr_is_never_null_inner_spill_fill(void) +{ + asm volatile (" \ + r1 = 0; \ + *(u32*)(r10 - 4) = r1; \ + r2 = r10; \ + r2 += -4; \ + r1 = %[map_in_map] ll; \ + call %[bpf_map_lookup_elem]; \ + if r0 != 0 goto l0_%=; \ + exit; \ +l0_%=: *(u64 *)(r10 -16) = r0; \ + r1 = *(u64 *)(r10 -16); \ + if r1 == 0 goto l1_%=; \ + exit; \ +l1_%=: r10 = 42; \ + exit; \ +" : + : __imm(bpf_map_lookup_elem), + __imm_addr(map_in_map) + : __clobber_all); +} + +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_RINGBUF); + __uint(max_entries, 64 * 1024); + }); +} rb_in_map SEC(".maps"); + +struct rb_ctx { + void *rb; + struct bpf_dynptr dptr; +}; + +static __always_inline struct rb_ctx __rb_event_reserve(__u32 sz) +{ + struct rb_ctx rb_ctx = {}; + void *rb; + __u32 cpu = bpf_get_smp_processor_id(); + __u32 rb_slot = cpu & 1; + + rb = bpf_map_lookup_elem(&rb_in_map, &rb_slot); + if (!rb) + return rb_ctx; + + rb_ctx.rb = rb; + bpf_ringbuf_reserve_dynptr(rb, sz, 0, &rb_ctx.dptr); + + return rb_ctx; +} + +static __noinline void __rb_event_submit(struct rb_ctx *ctx) +{ + if (!ctx->rb) + return; + + /* If the verifier (incorrectly) concludes that ctx->rb can be + * NULL at this point, we'll get "BPF_EXIT instruction in main + * prog would lead to reference leak" error + */ + bpf_ringbuf_submit_dynptr(&ctx->dptr, 0); +} + +SEC("socket") +int map_ptr_is_never_null_rb(void *ctx) +{ + struct rb_ctx event_ctx = __rb_event_reserve(256); + __rb_event_submit(&event_ctx); + return 0; +} + char _license[] SEC("license") = "GPL"; -- 2.47.1
