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bpf: Check scalar or invalid register in check_helper_mem_access

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Move the check for a NULL or zero register to check_helper_mem_access. This
makes check_stack_boundary easier to understand.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-3-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2020-09-21 13:12:18 +01:00 committed by Alexei Starovoitov
parent 2af30f115d
commit 0d004c020b
1 changed files with 11 additions and 13 deletions
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24
kernel/bpf/verifier.c
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@ -3641,18 +3641,6 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
struct bpf_func_state *state = func(env, reg); struct bpf_func_state *state = func(env, reg);
int err, min_off, max_off, i, j, slot, spi; int err, min_off, max_off, i, j, slot, spi;
if (reg->type != PTR_TO_STACK) {
/* Allow zero-byte read from NULL, regardless of pointer type */
if (zero_size_allowed && access_size == 0 &&
register_is_null(reg))
return 0;
verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[reg->type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
}
if (tnum_is_const(reg->var_off)) { if (tnum_is_const(reg->var_off)) {
min_off = max_off = reg->var_off.value + reg->off; min_off = max_off = reg->var_off.value + reg->off;
err = __check_stack_boundary(env, regno, min_off, access_size, err = __check_stack_boundary(env, regno, min_off, access_size,
@ -3797,9 +3785,19 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
access_size, zero_size_allowed, access_size, zero_size_allowed,
"rdwr", "rdwr",
&env->prog->aux->max_rdwr_access); &env->prog->aux->max_rdwr_access);
default: /* scalar_value|ptr_to_stack or invalid ptr */ case PTR_TO_STACK:
return check_stack_boundary(env, regno, access_size, return check_stack_boundary(env, regno, access_size,
zero_size_allowed, meta); zero_size_allowed, meta);
default: /* scalar_value or invalid ptr */
/* Allow zero-byte read from NULL, regardless of pointer type */
if (zero_size_allowed && access_size == 0 &&
register_is_null(reg))
return 0;
verbose(env, "R%d type=%s expected=%s\n", regno,
reg_type_str[reg->type],
reg_type_str[PTR_TO_STACK]);
return -EACCES;
} }
} }