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Wed, 21 Oct 2026 01:01:20 -0700 (PDT) Received: from Terra.tail0ac356.ts.net ([198.176.50.208]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-367416a1fb9sm4470610eec.20.2026.10.21.01.01.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 01:01:19 -0700 (PDT) From: Weiming Shi To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Shuah Khan Cc: bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, co+eada64ce90ecebce@bugs.sh, Xiang Mei , Weiming Shi , Alexei Starovoitov Subject: [PATCH bpf v2 2/2] selftests/bpf: Test missing and callback stack arguments Date: Wed, 21 Oct 2026 01:01:00 -0700 Message-ID: <20261021080100.2663618-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261021080100.2663618-1-bestswngs@gmail.com> References: <20261021080100.2663618-1-bestswngs@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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(). Expect the verifier to reject the second r11 load at offset 16. Also exercise synchronous and asynchronous callbacks whose BTF prototypes declare a sixth argument. Initialize the outgoing slot at each helper call site so the programs reach the callback-specific rejection. Keep a valid six-argument direct call in each program so bpf_fixup_call_args() records the stack-argument requirement and cannot become an unrelated rejection fallback. The fix also rejects the existing uninitialized-stack-argument test before the later unreadable-register check. Update that test's expected diagnostic accordingly. Suggested-by: Alexei Starovoitov Assisted-by: LLM Signed-off-by: Weiming Shi --- Changes in v2: - Add synchronous bpf_loop callback coverage. - Add asynchronous bpf_timer callback coverage. - Add the six-argument callback BTF prototype and initialize the outgoing stack slot so both tests reach the callback-specific rejection. .../bpf/progs/btf__verifier_stack_arg_order.c | 10 ++ .../bpf/progs/verifier_stack_arg_order.c | 121 +++++++++++++++++- 2 files changed, 130 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/btf__verifier_stack_arg_order.c b/tools/testing/selftests/bpf/progs/btf__verifier_stack_arg_order.c index 99bc115f8380a7..cd0ab034b788ce 100644 --- a/tools/testing/selftests/bpf/progs/btf__verifier_stack_arg_order.c +++ b/tools/testing/selftests/bpf/progs/btf__verifier_stack_arg_order.c @@ -25,6 +25,11 @@ void subprog_bad_ptr_7args(long *a, int b, int c, int d, int e, int f, int g) { } +int callback_6args(long a, long b, long c, long d, long e, long f) +{ + return a + b + c + d + e + f; +} + #else int subprog_bad_order_6args(void) @@ -46,4 +51,9 @@ void subprog_bad_ptr_7args(void) { } +int callback_6args(void) +{ + return 0; +} + #endif 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 c9fe4857da3f55..610c96e8113760 100644 --- a/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c +++ b/tools/testing/selftests/bpf/progs/verifier_stack_arg_order.c @@ -5,6 +5,17 @@ #include #include "bpf_misc.h" +struct timer_value { + struct bpf_timer timer; +}; + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, int); + __type(value, struct timer_value); +} timer_map SEC(".maps"); + #if (defined(__TARGET_ARCH_x86) || defined(__TARGET_ARCH_arm64)) && \ defined(__BPF_FEATURE_STACK_ARGUMENT) @@ -129,6 +140,25 @@ static void subprog_bad_ptr_7args(long *a, int b, int c, int d, int e, int f, in ); } +__noinline __used __naked +static int callback_6args(long a, long b, long c, long d, long e, long f) +{ + asm volatile ("r0 = *(u64 *)(r11 + 8);" + "exit;" + ::: __clobber_all + ); +} + +__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 +181,7 @@ __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 +200,95 @@ __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 + ); +} + +SEC("tc") +__description("stack_arg: synchronous callback with stack args") +__failure +__msg("callback subprog cannot have stack args") +__btf_func_path("btf__verifier_stack_arg_order.bpf.o") +__naked void stack_arg_sync_callback(void) +{ + asm volatile ("r6 = 0;" + "*(u64 *)(r11 - 8) = r6;" + "r1 = 1;" + "r2 = %[callback_6args];" + "r3 = 0;" + "r4 = 0;" + "call %[bpf_loop];" + "r1 = 1;" + "r2 = 2;" + "r3 = 3;" + "r4 = 4;" + "r5 = 5;" + "*(u64 *)(r11 - 8) = 6;" + "call callback_6args;" + "r0 = 0;" + "exit;" + : + : __imm_ptr(callback_6args), + __imm(bpf_loop) + : __clobber_common, "r6" + ); +} + +SEC("tc") +__description("stack_arg: asynchronous callback with stack args") +__failure +__msg("callback subprog cannot have stack args") +__btf_func_path("btf__verifier_stack_arg_order.bpf.o") +__naked void stack_arg_async_callback(void) +{ + asm volatile ("r1 = 0;" + "*(u32 *)(r10 - 4) = r1;" + "r1 = %[timer_map] ll;" + "r2 = r10;" + "r2 += -4;" + "call %[bpf_map_lookup_elem];" + "if r0 == 0 goto l0_%=;" + "r6 = r0;" + "r7 = 0;" + "*(u64 *)(r11 - 8) = r7;" + "r1 = r6;" + "r2 = %[callback_6args];" + "call %[bpf_timer_set_callback];" + "r1 = 1;" + "r2 = 2;" + "r3 = 3;" + "r4 = 4;" + "r5 = 5;" + "*(u64 *)(r11 - 8) = 6;" + "call callback_6args;" + "l0_%=: r0 = 0;" + "exit;" + : + : __imm_addr(timer_map), + __imm_ptr(callback_6args), + __imm(bpf_map_lookup_elem), + __imm(bpf_timer_set_callback) + : __clobber_common, "r6", "r7" + ); +} + #else SEC("socket") -- 2.56.0