Add BPF verifier support for single- and multi-level pointer parameters and return values in BPF trampolines by treating these parameters as SCALAR_VALUE. This extends the existing support for int and void pointers that are already treated as SCALAR_VALUE. This provides consistent logic for single and multi-level pointers: if a type is treated as SCALAR for a single-level pointer, the same applies to multi-level pointers. The exception is pointer-to-struct, which is currently PTR_TO_BTF_ID for single-level but treated as scalar for multi-level pointers since the verifier lacks context to infer the size of target memory regions. Safety is ensured by existing BTF verification, which rejects invalid pointer types at the BTF verification stage. Signed-off-by: Slava Imameev --- kernel/bpf/btf.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 09fcbb125155..524bb2d6d964 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6508,13 +6508,6 @@ struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog) return prog->aux->attach_btf; } -static bool is_void_or_int_ptr(struct btf *btf, const struct btf_type *t) -{ - /* skip modifiers */ - t = btf_type_skip_modifiers(btf, t->type, NULL); - return btf_type_is_void(t) || btf_type_is_int(t); -} - u32 btf_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, int off) { @@ -6903,10 +6896,14 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, } /* - * If it's a pointer to void, it's the same as scalar from the verifier - * safety POV. Either way, no futher pointer walking is allowed. + * If it's a single or multilevel pointer, except a pointer + * to a structure, it's the same as scalar from the verifier + * safety POV. Multilevel pointers to structures are treated as + * scalars. The verifier lacks the context to infer the size of + * their target memory regions. Either way, no further pointer + * walking is allowed. */ - if (is_void_or_int_ptr(btf, t)) + if (!btf_type_is_struct_ptr(btf, t)) return true; /* this is a pointer to another type */ -- 2.34.1 Add single and multi-level pointer parameters and return value test coverage for BPF trampolines. Includes verifier tests for single and multi-level pointers. The tests check verifier logs for pointers inferred as scalar() type. Signed-off-by: Slava Imameev --- net/bpf/test_run.c | 17 +++++ .../selftests/bpf/prog_tests/verifier.c | 2 + .../bpf/progs/verifier_ctx_ptr_param.c | 68 +++++++++++++++++++ 3 files changed, 87 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/verifier_ctx_ptr_param.c diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 56bc8dc1e281..14c4814a7dab 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -567,6 +567,23 @@ noinline void bpf_fentry_test_sinfo(struct skb_shared_info *sinfo) { } +noinline void bpf_fentry_test_ppvoid(void **pp) +{ +} + +noinline void bpf_fentry_test_pppvoid(void ***ppp) +{ +} + +noinline void bpf_fentry_test_ppfile(struct file **ppf) +{ +} + +noinline struct file **bpf_fexit_test_ret_ppfile(void) +{ + return (struct file **)NULL; +} + __bpf_kfunc int bpf_modify_return_test(int a, int *b) { *b += 1; diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c index 8cdfd74c95d7..bcf01cb4cfe4 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -115,6 +115,7 @@ #include "verifier_lsm.skel.h" #include "verifier_jit_inline.skel.h" #include "irq.skel.h" +#include "verifier_ctx_ptr_param.skel.h" #define MAX_ENTRIES 11 @@ -259,6 +260,7 @@ void test_verifier_lsm(void) { RUN(verifier_lsm); } void test_irq(void) { RUN(irq); } void test_verifier_mtu(void) { RUN(verifier_mtu); } void test_verifier_jit_inline(void) { RUN(verifier_jit_inline); } +void test_verifier_ctx_ptr_param(void) { RUN(verifier_ctx_ptr_param); } static int init_test_val_map(struct bpf_object *obj, char *map_name) { diff --git a/tools/testing/selftests/bpf/progs/verifier_ctx_ptr_param.c b/tools/testing/selftests/bpf/progs/verifier_ctx_ptr_param.c new file mode 100644 index 000000000000..b507dc850543 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/verifier_ctx_ptr_param.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Verifier tests for single- and multi-level pointer parameter handling + * Copyright (c) 2026 CrowdStrike, Inc. + */ + +#include +#include +#include +#include "bpf_misc.h" + +SEC("fentry/bpf_fentry_test_ppvoid") +__description("fentry/void**: void ** inferred as scalar") +__success __retval(0) +__log_level(2) +__msg("R1=ctx() R2=scalar()") +__naked void fentry_ppvoid_as_scalar(void) +{ + asm volatile (" \ + r2 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ + " ::: __clobber_all); +} + +SEC("fentry/bpf_fentry_test_pppvoid") +__description("fentry/void***: void *** inferred as scalar") +__success __retval(0) +__log_level(2) +__msg("R1=ctx() R2=scalar()") +__naked void fentry_pppvoid_as_scalar(void) +{ + asm volatile (" \ + r2 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ + " ::: __clobber_all); +} + +SEC("fentry/bpf_fentry_test_ppfile") +__description("fentry/struct file***: struct file *** inferred as scalar") +__success __retval(0) +__log_level(2) +__msg("R1=ctx() R2=scalar()") +__naked void fentry_ppfile_as_scalar(void) +{ + asm volatile (" \ + r2 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ + " ::: __clobber_all); +} + +SEC("fexit/bpf_fexit_test_ret_ppfile") +__description("fexit/return struct file**: returned struct file ** inferred as scalar") +__success __retval(0) +__log_level(2) +__msg("R1=ctx() R2=scalar()") +__naked void fexit_ppfile_as_scalar(void) +{ + asm volatile (" \ + r2 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ + " ::: __clobber_all); +} + +char _license[] SEC("license") = "GPL"; -- 2.34.1