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Wed, 07 Oct 2026 10:42:21 -0700 (PDT) From: Weiming Shi To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH bpf 2/2] selftests/bpf: Test missing caller stack argument slots Date: Thu, 8 Oct 2026 01:42:03 +0800 Message-ID: <20261007174203.37071-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261007174203.37071-1-bestswngs@gmail.com> References: <20261007174203.37071-1-bestswngs@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Exercise the path where a static seven-argument subprogram has unreliable BTF and is called through a bridge with only one initialized outgoing stack argument. The callee expects two stack arguments, but the unreliable-BTF path skips check_outgoing_stack_args(). Without the fix, the second r11 load copies an 80-byte bpf_reg_state from stack_arg_regs[1], past the caller's one-element array. Expect the verifier to reject that load at offset 16. The fix also rejects the existing uninitialized-stack-argument test before the later unreadable-register check. Update that test's expected diagnostic accordingly. Assisted-by: LLM Signed-off-by: Weiming Shi --- .../bpf/progs/verifier_stack_arg_order.c | 33 ++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c b/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c index c9fe4857d..23c7515ea 100644 --- a/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c +++ b/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c @@ -129,6 +129,16 @@ static void subprog_bad_ptr_7args(long *a, int b, int c, int d, int e, int f, in ); } +__noinline __used __naked +static void subprog_call_bad_ptr_7args(void) +{ + asm volatile ("*(u64 *)(r11 - 8) = 0;" + "call subprog_bad_ptr_7args;" + "exit;" + ::: __clobber_all + ); +} + SEC("tc") __description("stack_arg: read without caller write") __failure @@ -151,7 +161,7 @@ __naked void stack_arg_read_without_write_1(void) SEC("tc") __description("stack_arg: read with not-initialized caller write") __failure -__msg("R0 !read_ok") +__msg("invalid read from uninitialized stack arg off 8") __btf_func_path("btf__verifier_stack_arg_order.bpf.o") __naked void stack_arg_read_without_write_2(void) { @@ -170,6 +180,27 @@ __naked void stack_arg_read_without_write_2(void) ); } +SEC("tc") +__description("stack_arg: unreliable callee with too few stack args") +__failure +__msg("invalid read from uninitialized stack arg off 16") +__btf_func_path("btf__verifier_stack_arg_order.bpf.o") +__naked void stack_arg_read_with_short_bridge_write(void) +{ + asm volatile ("r1 = 0;" + "r2 = 0;" + "r3 = 0;" + "r4 = 0;" + "r5 = 0;" + "*(u64 *)(r11 - 8) = 0;" + "*(u64 *)(r11 - 16) = 0;" + "call subprog_bad_ptr_7args;" + "call subprog_call_bad_ptr_7args;" + "exit;" + ::: __clobber_all + ); +} + #else SEC("socket") -- 2.55.0