From 8aeaed21befc90f27f4fca6dd190850d97d2e9e3 Mon Sep 17 00:00:00 2001 From: Philo Lu Date: Wed, 11 Sep 2024 11:37:15 +0800 Subject: bpf: Support __nullable argument suffix for tp_btf Pointers passed to tp_btf were trusted to be valid, but some tracepoints do take NULL pointer as input, such as trace_tcp_send_reset(). Then the invalid memory access cannot be detected by verifier. This patch fix it by add a suffix "__nullable" to the unreliable argument. The suffix is shown in btf, and PTR_MAYBE_NULL will be added to nullable arguments. Then users must check the pointer before use it. A problem here is that we use "btf_trace_##call" to search func_proto. As it is a typedef, argument names as well as the suffix are not recorded. To solve this, I use bpf_raw_event_map to find "__bpf_trace##template" from "btf_trace_##call", and then we can see the suffix. Suggested-by: Alexei Starovoitov Signed-off-by: Philo Lu Link: https://lore.kernel.org/r/20240911033719.91468-2-lulie@linux.alibaba.com Signed-off-by: Martin KaFai Lau --- kernel/bpf/btf.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'kernel/bpf/btf.c') diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 520f49f422fe..7e03a98ccb7c 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6523,6 +6523,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, if (prog_args_trusted(prog)) info->reg_type |= PTR_TRUSTED; + if (btf_param_match_suffix(btf, &args[arg], "__nullable")) + info->reg_type |= PTR_MAYBE_NULL; + if (tgt_prog) { enum bpf_prog_type tgt_type; -- cgit v1.2.3