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bpf: Reduce stack consumption in check_stack_write_fixed_off

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The fake_reg moved into env->fake_reg given it consumes a lot of stack
space (120 bytes). Migrate the fake_reg in check_stack_write_fixed_off()
as well now that we have it.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20240613115310.25383-2-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2024-06-13 13:53:09 +02:00 committed by Alexei Starovoitov
parent 9242480126
commit e73cd1cfc2
1 changed files with 5 additions and 4 deletions
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9
kernel/bpf/verifier.c
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@ -4549,11 +4549,12 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
state->stack[spi].spilled_ptr.id = 0;
} else if (!reg && !(off % BPF_REG_SIZE) && is_bpf_st_mem(insn) &&
env->bpf_capable) {
struct bpf_reg_state fake_reg = {};
struct bpf_reg_state *tmp_reg = &env->fake_reg[0];
__mark_reg_known(&fake_reg, insn->imm);
fake_reg.type = SCALAR_VALUE;
save_register_state(env, state, spi, &fake_reg, size);
memset(tmp_reg, 0, sizeof(*tmp_reg));
__mark_reg_known(tmp_reg, insn->imm);
tmp_reg->type = SCALAR_VALUE;
save_register_state(env, state, spi, tmp_reg, size);
} else if (reg && is_spillable_regtype(reg->type)) {
/* register containing pointer is being spilled into stack */
if (size != BPF_REG_SIZE) {