From 4137bbd9af1f80f86419097d728e6af136e4fea8 Mon Sep 17 00:00:00 2001 From: Yiyang Chen Date: Tue, 30 Jun 2026 08:41:27 +0000 Subject: [PATCH] selftests/bpf: Cover MEM_ALLOC access past object bounds Add a linked_list negative loader case for a program-BTF type whose last member is a zero-length flexible array. The program writes through the first flexible-array element of an object allocated by bpf_obj_new(). The verifier should reject the access when the BTF walk reaches beyond the static size of the allocated object. Signed-off-by: Yiyang Chen Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/e36fd5d2f4047809f0e5da46a7077083297e64db.1782807039.git.chenyy23@mails.tsinghua.edu.cn Signed-off-by: Kumar Kartikeya Dwivedi --- .../selftests/bpf/prog_tests/linked_list.c | 1 + .../selftests/bpf/progs/linked_list_fail.c | 23 +++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c index 8defea0253ed..c3d133c6a00d 100644 --- a/tools/testing/selftests/bpf/prog_tests/linked_list.c +++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c @@ -68,6 +68,7 @@ static struct { { "obj_type_id_oor", "local type ID argument must be in range [0, U32_MAX]" }, { "obj_new_no_composite", "bpf_obj_new/bpf_percpu_obj_new type ID argument must be of a struct" }, { "obj_new_no_struct", "bpf_obj_new/bpf_percpu_obj_new type ID argument must be of a struct" }, + { "obj_new_flex_array", "access beyond struct obj_new_flex" }, { "obj_drop_non_zero_off", "R1 must have zero offset when passed to release func" }, { "new_null_ret", "R0 invalid mem access 'ptr_or_null_'" }, { "obj_new_acq", "Unreleased reference id=" }, diff --git a/tools/testing/selftests/bpf/progs/linked_list_fail.c b/tools/testing/selftests/bpf/progs/linked_list_fail.c index ddd26d1a083f..031e77a288ee 100644 --- a/tools/testing/selftests/bpf/progs/linked_list_fail.c +++ b/tools/testing/selftests/bpf/progs/linked_list_fail.c @@ -167,6 +167,16 @@ CHECK_OP(push_back); #undef CHECK_OP #undef INIT +struct obj_new_flex_elem { + int lo; + int hi; +}; + +struct obj_new_flex { + int hdr; + struct obj_new_flex_elem cells[]; +}; + SEC("?kprobe/xyz") int map_compat_kprobe(void *ctx) { @@ -230,6 +240,19 @@ int obj_new_no_struct(void *ctx) return 0; } +SEC("?tc") +int obj_new_flex_array(void *ctx) +{ + struct obj_new_flex *p; + + p = bpf_obj_new_impl(bpf_core_type_id_local(struct obj_new_flex), NULL); + if (!p) + return 0; + p->cells[0].hi = 42; + bpf_obj_drop_impl(p, NULL); + return 0; +} + SEC("?tc") int obj_drop_non_zero_off(void *ctx) {