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Merge branch 'bpf-some-fixes-for-nullness-elision'

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Daniel Xu says:

====================
Tow fixes for nullness elision.

Changes from v1:
* Reword commit message in patch 1
* Add tags
====================

Link: https://patch.msgid.link/cover.1738689872.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2025-02-07 15:45:44 -08:00
commit 310794c219
2 changed files with 36 additions and 8 deletions
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29
kernel/bpf/verifier.c
View file

@ -9149,10 +9149,11 @@ static int check_reg_const_str(struct bpf_verifier_env *env,
return 0;
}
/* Returns constant key value if possible, else negative error */
static s64 get_constant_map_key(struct bpf_verifier_env *env,
/* Returns constant key value in `value` if possible, else negative error */
static int get_constant_map_key(struct bpf_verifier_env *env,
struct bpf_reg_state *key,
u32 key_size)
u32 key_size,
s64 *value)
{
struct bpf_func_state *state = func(env, key);
struct bpf_reg_state *reg;
@ -9179,8 +9180,10 @@ static s64 get_constant_map_key(struct bpf_verifier_env *env,
/* First handle precisely tracked STACK_ZERO */
for (i = off; i >= 0 && stype[i] == STACK_ZERO; i--)
zero_size++;
if (zero_size >= key_size)
if (zero_size >= key_size) {
*value = 0;
return 0;
}
/* Check that stack contains a scalar spill of expected size */
if (!is_spilled_scalar_reg(&state->stack[spi]))
@ -9203,9 +9206,12 @@ static s64 get_constant_map_key(struct bpf_verifier_env *env,
if (err < 0)
return err;
return reg->var_off.value;
*value = reg->var_off.value;
return 0;
}
static bool can_elide_value_nullness(enum bpf_map_type type);
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
const struct bpf_func_proto *fn,
@ -9354,9 +9360,16 @@ skip_type_check:
err = check_helper_mem_access(env, regno, key_size, BPF_READ, false, NULL);
if (err)
return err;
meta->const_map_key = get_constant_map_key(env, reg, key_size);
if (meta->const_map_key < 0 && meta->const_map_key != -EOPNOTSUPP)
return meta->const_map_key;
if (can_elide_value_nullness(meta->map_ptr->map_type)) {
err = get_constant_map_key(env, reg, key_size, &meta->const_map_key);
if (err < 0) {
meta->const_map_key = -1;
if (err == -EOPNOTSUPP)
err = 0;
else
return err;
}
}
break;
case ARG_PTR_TO_MAP_VALUE:
if (type_may_be_null(arg_type) && register_is_null(reg))

15
tools/testing/selftests/bpf/progs/verifier_array_access.c
View file

@ -713,4 +713,19 @@ unsigned int non_stack_key_lookup(void)
return val->index;
}
SEC("socket")
__description("doesn't reject UINT64_MAX as s64 for irrelevant maps")
__success __retval(42)
unsigned int doesnt_reject_irrelevant_maps(void)
{
__u64 key = 0xFFFFFFFFFFFFFFFF;
struct test_val *val;
val = bpf_map_lookup_elem(&map_hash_48b, &key);
if (val)
return val->index;
return 42;
}
char _license[] SEC("license") = "GPL";