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bpf: verifier: centralize const dynptr check in unmark_stack_slots_dynptr()

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Move the const dynptr check into unmark_stack_slots_dynptr() so callers
don’t have to duplicate it. This puts the validation next to the code
that manipulates dynptr stack slots and allows upcoming changes to reuse
it directly.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251026203853.135105-6-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Mykyta Yatsenko 2025-10-26 20:38:48 +00:00 committed by Alexei Starovoitov
parent 5a5fff604f
commit 9cba966f1c
1 changed files with 9 additions and 8 deletions
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17
kernel/bpf/verifier.c
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@ -828,6 +828,15 @@ static int unmark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_re
struct bpf_func_state *state = func(env, reg);
int spi, ref_obj_id, i;
/*
* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
* be released by any dynptr helper. Hence, unmark_stack_slots_dynptr
* is safe to do directly.
*/
if (reg->type == CONST_PTR_TO_DYNPTR) {
verifier_bug(env, "CONST_PTR_TO_DYNPTR cannot be released");
return -EFAULT;
}
spi = dynptr_get_spi(env, reg);
if (spi < 0)
return spi;
@ -11514,15 +11523,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
if (meta.release_regno) {
err = -EINVAL;
/* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
* be released by any dynptr helper. Hence, unmark_stack_slots_dynptr
* is safe to do directly.
*/
if (arg_type_is_dynptr(fn->arg_type[meta.release_regno - BPF_REG_1])) {
if (regs[meta.release_regno].type == CONST_PTR_TO_DYNPTR) {
verifier_bug(env, "CONST_PTR_TO_DYNPTR cannot be released");
return -EFAULT;
}
err = unmark_stack_slots_dynptr(env, &regs[meta.release_regno]);
} else if (func_id == BPF_FUNC_kptr_xchg && meta.ref_obj_id) {
u32 ref_obj_id = meta.ref_obj_id;