From 77515ab12e4983e6416f8c35039a3f0c0822ac70 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Thu, 3 Sep 2026 16:44:19 +0200 Subject: [PATCH] bpf: Mark signal tracepoint siginfo arguments as scalar The signal_generate and signal_deliver tracepoints declare their info argument as a struct kernel_siginfo pointer. btf_ctx_access() therefore treats it as a trusted pointer for tp_btf programs. Signal delivery also uses SEND_SIG_NOINFO and SEND_SIG_PRIV as special values for this argument. Those values are zero and one respectively, and are not pointers. A tp_btf program can currently dereference either value and fault the kernel. In particular, signal_generate can run from timer interrupt context, turning the fault into a kernel panic. Record both tracepoints in raw_tp_null_args[] and mark argument one as a non-pointer. This preserves scalar access to the cookie while rejecting direct and helper-mediated pointer use. Merely marking it nullable would not suffice because SEND_SIG_PRIV is nonzero. Fixes: 838a10bd2ebf ("bpf: Augment raw_tp arguments with PTR_MAYBE_NULL") Reported-by: Nicholas Carlini Suggested-by: Nicholas Carlini Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260903144433.1716731-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/btf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 85ae92c920e4..b5aa802451bd 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6732,6 +6732,9 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = { { "rxrpc_resend", 0x10 }, { "rxrpc_tq", 0x10 }, { "rxrpc_client", 0x1 }, + /* signal */ + { "signal_generate", 0x20 }, + { "signal_deliver", 0x20 }, /* skb */ {"kfree_skb", 0x1000}, /* sunrpc */