From: Emil Tsalapatis <emil@etsalapatis.com>
To: bpf@vger.kernel.org
Cc: andrii@kernel.org, ast@kernel.org, daniel@iogearbox.net,
eddyz87@gmail.com, martin.lau@kernel.org, memxor@gmail.com,
song@kernel.org, yonghong.song@linux.dev,
Emil Tsalapatis <emil@etsalapatis.com>
Subject: [PATCH bpf-next v5 1/5] bpf: Factor out program return value calculation
Date: Fri, 27 Feb 2026 10:46:12 -0500 [thread overview]
Message-ID: <20260227154616.6846-2-emil@etsalapatis.com> (raw)
In-Reply-To: <20260227154616.6846-1-emil@etsalapatis.com>
Factor the return value range calculation logic in check_return_code
out of the function in preparation for separating the return value
validation logic for BPF_EXIT and bpf_throw().
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/verifier.c | 225 +++++++++++++++++++----------------
2 files changed, 126 insertions(+), 100 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index ef8e45a362d9..0e639613d8cf 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -266,6 +266,7 @@ struct bpf_reference_state {
struct bpf_retval_range {
s32 minval;
s32 maxval;
+ bool return_32bit;
};
/* state of the program:
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index edf5342b982f..6cf2270c343c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2925,7 +2925,11 @@ static void init_reg_state(struct bpf_verifier_env *env,
static struct bpf_retval_range retval_range(s32 minval, s32 maxval)
{
- return (struct bpf_retval_range){ minval, maxval };
+ /*
+ * return_32bit is set to false by default and set explicitly
+ * by the caller when necessary.
+ */
+ return (struct bpf_retval_range){ minval, maxval, false };
}
#define BPF_MAIN_FUNC (-1)
@@ -11146,10 +11150,9 @@ static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env)
return is_rbtree_lock_required_kfunc(kfunc_btf_id);
}
-static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg,
- bool return_32bit)
+static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state *reg)
{
- if (return_32bit)
+ if (range.return_32bit)
return range.minval <= reg->s32_min_value && reg->s32_max_value <= range.maxval;
else
return range.minval <= reg->smin_value && reg->smax_value <= range.maxval;
@@ -11193,7 +11196,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
return err;
/* enforce R0 return value range, and bpf_callback_t returns 64bit */
- if (!retval_range_within(callee->callback_ret_range, r0, false)) {
+ if (!retval_range_within(callee->callback_ret_range, r0)) {
verbose_invalid_scalar(env, r0, callee->callback_ret_range,
"At callback return", "R0");
return -EINVAL;
@@ -17837,6 +17840,115 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
return 0;
}
+
+static bool return_retval_range(struct bpf_verifier_env *env, struct bpf_retval_range *range)
+{
+ enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
+
+ /* Default return value range. */
+ *range = retval_range(0, 1);
+
+ switch (prog_type) {
+ case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
+ switch (env->prog->expected_attach_type) {
+ case BPF_CGROUP_UDP4_RECVMSG:
+ case BPF_CGROUP_UDP6_RECVMSG:
+ case BPF_CGROUP_UNIX_RECVMSG:
+ case BPF_CGROUP_INET4_GETPEERNAME:
+ case BPF_CGROUP_INET6_GETPEERNAME:
+ case BPF_CGROUP_UNIX_GETPEERNAME:
+ case BPF_CGROUP_INET4_GETSOCKNAME:
+ case BPF_CGROUP_INET6_GETSOCKNAME:
+ case BPF_CGROUP_UNIX_GETSOCKNAME:
+ *range = retval_range(1, 1);
+ break;
+ case BPF_CGROUP_INET4_BIND:
+ case BPF_CGROUP_INET6_BIND:
+ *range = retval_range(0, 3);
+ break;
+ default:
+ break;
+ }
+ break;
+ case BPF_PROG_TYPE_CGROUP_SKB:
+ if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS)
+ *range = retval_range(0, 3);
+ break;
+ case BPF_PROG_TYPE_CGROUP_SOCK:
+ case BPF_PROG_TYPE_SOCK_OPS:
+ case BPF_PROG_TYPE_CGROUP_DEVICE:
+ case BPF_PROG_TYPE_CGROUP_SYSCTL:
+ case BPF_PROG_TYPE_CGROUP_SOCKOPT:
+ break;
+ case BPF_PROG_TYPE_RAW_TRACEPOINT:
+ if (!env->prog->aux->attach_btf_id)
+ return false;
+ *range = retval_range(0, 0);
+ break;
+ case BPF_PROG_TYPE_TRACING:
+ switch (env->prog->expected_attach_type) {
+ case BPF_TRACE_FENTRY:
+ case BPF_TRACE_FEXIT:
+ case BPF_TRACE_FSESSION:
+ *range = retval_range(0, 0);
+ break;
+ case BPF_TRACE_RAW_TP:
+ case BPF_MODIFY_RETURN:
+ return false;
+ case BPF_TRACE_ITER:
+ break;
+ default:
+ }
+ break;
+ case BPF_PROG_TYPE_KPROBE:
+ switch (env->prog->expected_attach_type) {
+ case BPF_TRACE_KPROBE_SESSION:
+ case BPF_TRACE_UPROBE_SESSION:
+ break;
+ default:
+ return false;
+ }
+ break;
+ case BPF_PROG_TYPE_SK_LOOKUP:
+ *range = retval_range(SK_DROP, SK_PASS);
+ break;
+
+ case BPF_PROG_TYPE_LSM:
+ if (env->prog->expected_attach_type != BPF_LSM_CGROUP) {
+ /* no range found, any return value is allowed */
+ if (!get_func_retval_range(env->prog, range))
+ return false;
+ /* no restricted range, any return value is allowed */
+ if (range->minval == S32_MIN && range->maxval == S32_MAX)
+ return false;
+ range->return_32bit = true;
+ } else if (!env->prog->aux->attach_func_proto->type) {
+ /* Make sure programs that attach to void
+ * hooks don't try to modify return value.
+ */
+ *range = retval_range(1, 1);
+ }
+ break;
+
+ case BPF_PROG_TYPE_NETFILTER:
+ *range = retval_range(NF_DROP, NF_ACCEPT);
+ break;
+ case BPF_PROG_TYPE_STRUCT_OPS:
+ *range = retval_range(0, 0);
+ break;
+ case BPF_PROG_TYPE_EXT:
+ /* freplace program can return anything as its return value
+ * depends on the to-be-replaced kernel func or bpf program.
+ */
+ default:
+ return false;
+ }
+
+ /* Continue calculating. */
+
+ return true;
+}
+
static int check_return_code(struct bpf_verifier_env *env, int regno, const char *reg_name)
{
const char *exit_ctx = "At program exit";
@@ -17845,7 +17957,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_retval_range range = retval_range(0, 1);
enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
- int err;
+ int ret, err;
struct bpf_func_state *frame = env->cur_state->frame[0];
const bool is_subprog = frame->subprogno;
bool return_32bit = false;
@@ -17856,7 +17968,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
switch (prog_type) {
case BPF_PROG_TYPE_LSM:
if (prog->expected_attach_type == BPF_LSM_CGROUP)
- /* See below, can be 0 or 0-1 depending on hook. */
+ /* See return_retval_range, can be 0 or 0-1 depending on hook. */
break;
if (!prog->aux->attach_func_proto->type)
return 0;
@@ -17914,101 +18026,14 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
return 0;
}
- switch (prog_type) {
- case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
- if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
- env->prog->expected_attach_type == BPF_CGROUP_UDP6_RECVMSG ||
- env->prog->expected_attach_type == BPF_CGROUP_UNIX_RECVMSG ||
- env->prog->expected_attach_type == BPF_CGROUP_INET4_GETPEERNAME ||
- env->prog->expected_attach_type == BPF_CGROUP_INET6_GETPEERNAME ||
- env->prog->expected_attach_type == BPF_CGROUP_UNIX_GETPEERNAME ||
- env->prog->expected_attach_type == BPF_CGROUP_INET4_GETSOCKNAME ||
- env->prog->expected_attach_type == BPF_CGROUP_INET6_GETSOCKNAME ||
- env->prog->expected_attach_type == BPF_CGROUP_UNIX_GETSOCKNAME)
- range = retval_range(1, 1);
- if (env->prog->expected_attach_type == BPF_CGROUP_INET4_BIND ||
- env->prog->expected_attach_type == BPF_CGROUP_INET6_BIND)
- range = retval_range(0, 3);
- break;
- case BPF_PROG_TYPE_CGROUP_SKB:
- if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
- range = retval_range(0, 3);
- enforce_attach_type_range = tnum_range(2, 3);
- }
- break;
- case BPF_PROG_TYPE_CGROUP_SOCK:
- case BPF_PROG_TYPE_SOCK_OPS:
- case BPF_PROG_TYPE_CGROUP_DEVICE:
- case BPF_PROG_TYPE_CGROUP_SYSCTL:
- case BPF_PROG_TYPE_CGROUP_SOCKOPT:
- break;
- case BPF_PROG_TYPE_RAW_TRACEPOINT:
- if (!env->prog->aux->attach_btf_id)
- return 0;
- range = retval_range(0, 0);
- break;
- case BPF_PROG_TYPE_TRACING:
- switch (env->prog->expected_attach_type) {
- case BPF_TRACE_FENTRY:
- case BPF_TRACE_FEXIT:
- case BPF_TRACE_FSESSION:
- range = retval_range(0, 0);
- break;
- case BPF_TRACE_RAW_TP:
- case BPF_MODIFY_RETURN:
- return 0;
- case BPF_TRACE_ITER:
- break;
- default:
- return -ENOTSUPP;
- }
- break;
- case BPF_PROG_TYPE_KPROBE:
- switch (env->prog->expected_attach_type) {
- case BPF_TRACE_KPROBE_SESSION:
- case BPF_TRACE_UPROBE_SESSION:
- range = retval_range(0, 1);
- break;
- default:
- return 0;
- }
- break;
- case BPF_PROG_TYPE_SK_LOOKUP:
- range = retval_range(SK_DROP, SK_PASS);
- break;
+ if (prog_type == BPF_PROG_TYPE_STRUCT_OPS && !ret_type)
+ return 0;
- case BPF_PROG_TYPE_LSM:
- if (env->prog->expected_attach_type != BPF_LSM_CGROUP) {
- /* no range found, any return value is allowed */
- if (!get_func_retval_range(env->prog, &range))
- return 0;
- /* no restricted range, any return value is allowed */
- if (range.minval == S32_MIN && range.maxval == S32_MAX)
- return 0;
- return_32bit = true;
- } else if (!env->prog->aux->attach_func_proto->type) {
- /* Make sure programs that attach to void
- * hooks don't try to modify return value.
- */
- range = retval_range(1, 1);
- }
- break;
+ if (prog_type == BPF_PROG_TYPE_CGROUP_SKB && (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS))
+ enforce_attach_type_range = tnum_range(2, 3);
- case BPF_PROG_TYPE_NETFILTER:
- range = retval_range(NF_DROP, NF_ACCEPT);
- break;
- case BPF_PROG_TYPE_STRUCT_OPS:
- if (!ret_type)
- return 0;
- range = retval_range(0, 0);
- break;
- case BPF_PROG_TYPE_EXT:
- /* freplace program can return anything as its return value
- * depends on the to-be-replaced kernel func or bpf program.
- */
- default:
+ if (!return_retval_range(env, &range))
return 0;
- }
enforce_retval:
if (reg->type != SCALAR_VALUE) {
@@ -18021,7 +18046,7 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
if (err)
return err;
- if (!retval_range_within(range, reg, return_32bit)) {
+ if (!retval_range_within(range, reg)) {
verbose_invalid_scalar(env, reg, range, exit_ctx, reg_name);
if (!is_subprog &&
prog->expected_attach_type == BPF_LSM_CGROUP &&
--
2.49.0
next prev parent reply other threads:[~2026-02-27 15:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 15:46 [PATCH bpf-next v5 0/5] bpf: Allow void return type for global subprogs Emil Tsalapatis
2026-02-27 15:46 ` Emil Tsalapatis [this message]
2026-02-27 15:50 ` [PATCH bpf-next v5 1/5] bpf: Factor out program return value calculation Emil Tsalapatis
2026-02-27 18:57 ` Eduard Zingerman
2026-02-28 0:36 ` Emil Tsalapatis
2026-02-27 20:27 ` kernel test robot
2026-02-27 20:49 ` kernel test robot
2026-02-28 1:22 ` kernel test robot
2026-02-27 15:46 ` [PATCH bpf-next v5 2/5] bpf: Extract program_returns_void() for clarity Emil Tsalapatis
2026-02-27 15:46 ` [PATCH bpf-next v5 3/5] bpf: extract check_subprogram_return_code() " Emil Tsalapatis
2026-02-27 19:42 ` Eduard Zingerman
2026-02-27 15:46 ` [PATCH bpf-next v5 4/5] bpf: Allow void global functions in the verifier Emil Tsalapatis
2026-02-27 16:24 ` bot+bpf-ci
2026-02-27 19:32 ` Eduard Zingerman
2026-02-28 0:39 ` Emil Tsalapatis
2026-02-27 15:46 ` [PATCH bpf-next v5 5/5] selftests: bpf: Add tests for void global subprogs Emil Tsalapatis
2026-02-27 19:53 ` Eduard Zingerman
2026-02-28 0:32 ` Emil Tsalapatis
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