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bpf: Rework ptr_limit into alu_limit and add common error path

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commit b658bbb844e28f1862867f37e8ca11a8e2aa94a3 upstream.

Small refactor with no semantic changes in order to consolidate the max
ptr_limit boundary check.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Borkmann 2021-04-29 22:08:34 +00:00 committed by Greg Kroah-Hartman
parent f7fbedc909
commit 15de0c537b
1 changed files with 13 additions and 8 deletions
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21
kernel/bpf/verifier.c
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@ -4265,12 +4265,12 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
const struct bpf_reg_state *off_reg,
u32 *ptr_limit, u8 opcode)
u32 *alu_limit, u8 opcode)
{
bool off_is_neg = off_reg->smin_value < 0;
bool mask_to_left = (opcode == BPF_ADD && off_is_neg) ||
(opcode == BPF_SUB && !off_is_neg);
u32 off, max;
u32 off, max = 0, ptr_limit = 0;
if (!tnum_is_const(off_reg->var_off) &&
(off_reg->smin_value < 0) != (off_reg->smax_value < 0))
@ -4287,22 +4287,27 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
*/
off = ptr_reg->off + ptr_reg->var_off.value;
if (mask_to_left)
*ptr_limit = MAX_BPF_STACK + off;
ptr_limit = MAX_BPF_STACK + off;
else
*ptr_limit = -off - 1;
return *ptr_limit >= max ? -ERANGE : 0;
ptr_limit = -off - 1;
break;
case PTR_TO_MAP_VALUE:
max = ptr_reg->map_ptr->value_size;
if (mask_to_left) {
*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
ptr_limit = ptr_reg->umax_value + ptr_reg->off;
} else {
off = ptr_reg->smin_value + ptr_reg->off;
*ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
}
return *ptr_limit >= max ? -ERANGE : 0;
break;
default:
return -EINVAL;
}
if (ptr_limit >= max)
return -ERANGE;
*alu_limit = ptr_limit;
return 0;
}
static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,