[RFC PATCH bpf-next v2 07/11] bpf: Remove redundant dynptr arg check for helper
From: Amery Hung <hidden>
Date: 2026-03-07 06:44:49
Also in:
bpf
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
unmark_stack_slots_dynptr() already makes sure that CONST_PTR_TO_DYNPTR cannot be released. process_dynptr_func() also prevents passing uninitialized dynptr to helpers expecting initialized dynptr. Now that unmark_stack_slots_dynptr() also error returned from release_reference(), there should be no reason to keep these redundant checks. Signed-off-by: Amery Hung <redacted> --- kernel/bpf/verifier.c | 21 +------------------ .../testing/selftests/bpf/progs/dynptr_fail.c | 6 +++--- .../selftests/bpf/progs/user_ringbuf_fail.c | 4 ++-- 3 files changed, 6 insertions(+), 25 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0436fc4d9107..80b9ef6f329f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -9737,26 +9737,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, skip_type_check: if (arg_type_is_release(arg_type)) { - if (arg_type_is_dynptr(arg_type)) { - struct bpf_func_state *state = func(env, reg); - int spi; - - /* Only dynptr created on stack can be released, thus - * the get_spi and stack state checks for spilled_ptr - * should only be done before process_dynptr_func for - * PTR_TO_STACK. - */ - if (reg->type == PTR_TO_STACK) { - spi = dynptr_get_spi(env, reg); - if (spi < 0 || !state->stack[spi].spilled_ptr.id) { - verbose(env, "arg %d is an unacquired reference\n", regno); - return -EINVAL; - } - } else { - verbose(env, "cannot release unowned const bpf_dynptr\n"); - return -EINVAL; - } - } else if (!reg->ref_obj_id && !register_is_null(reg)) { + if (!arg_type_is_dynptr(arg_type) && !reg->ref_obj_id && !register_is_null(reg)) { verbose(env, "R%d must be referenced when passed to release function\n", regno); return -EINVAL;
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 5e1b1cf4ea8e..631e37500ec6 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c@@ -135,7 +135,7 @@ int ringbuf_missing_release_callback(void *ctx) /* Can't call bpf_ringbuf_submit/discard_dynptr on a non-initialized dynptr */ SEC("?raw_tp") -__failure __msg("arg 1 is an unacquired reference") +__failure __msg("Expected an initialized dynptr as arg #0") int ringbuf_release_uninit_dynptr(void *ctx) { struct bpf_dynptr ptr;
@@ -649,7 +649,7 @@ int invalid_offset(void *ctx) /* Can't release a dynptr twice */ SEC("?raw_tp") -__failure __msg("arg 1 is an unacquired reference") +__failure __msg("Expected an initialized dynptr as arg #0") int release_twice(void *ctx) { struct bpf_dynptr ptr;
@@ -676,7 +676,7 @@ static int release_twice_callback_fn(__u32 index, void *data) * within a callback function, fails */ SEC("?raw_tp") -__failure __msg("arg 1 is an unacquired reference") +__failure __msg("Expected an initialized dynptr as arg #0") int release_twice_callback(void *ctx) { struct bpf_dynptr ptr;
diff --git a/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c b/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c
index 54de0389f878..e8f4ae86470f 100644
--- a/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c
+++ b/tools/testing/selftests/bpf/progs/user_ringbuf_fail.c@@ -146,7 +146,7 @@ try_discard_dynptr(struct bpf_dynptr *dynptr, void *context) * not be able to read past the end of the pointer. */ SEC("?raw_tp") -__failure __msg("cannot release unowned const bpf_dynptr") +__failure __msg("cannot pass pointer to const bpf_dynptr, the helper mutates it") int user_ringbuf_callback_discard_dynptr(void *ctx) { bpf_user_ringbuf_drain(&user_ringbuf, try_discard_dynptr, NULL, 0);
@@ -166,7 +166,7 @@ try_submit_dynptr(struct bpf_dynptr *dynptr, void *context) * not be able to read past the end of the pointer. */ SEC("?raw_tp") -__failure __msg("cannot release unowned const bpf_dynptr") +__failure __msg("cannot pass pointer to const bpf_dynptr, the helper mutates it") int user_ringbuf_callback_submit_dynptr(void *ctx) { bpf_user_ringbuf_drain(&user_ringbuf, try_submit_dynptr, NULL, 0);
--
2.47.3