From 47e34cb74d376ddfeaef94abb1d6dfb3c905ee51 Mon Sep 17 00:00:00 2001 From: Dave Marchevsky Date: Mon, 12 Sep 2022 08:45:44 -0700 Subject: bpf: Add verifier check for BPF_PTR_POISON retval and arg BPF_PTR_POISON was added in commit c0a5a21c25f37 ("bpf: Allow storing referenced kptr in map") to denote a bpf_func_proto btf_id which the verifier will replace with a dynamically-determined btf_id at verification time. This patch adds verifier 'poison' functionality to BPF_PTR_POISON in order to prepare for expanded use of the value to poison ret- and arg-btf_id in ongoing work, namely rbtree and linked list patchsets [0, 1]. Specifically, when the verifier checks helper calls, it assumes that BPF_PTR_POISON'ed ret type will be replaced with a valid type before - or in lieu of - the default ret_btf_id logic. Similarly for arg btf_id. If poisoned btf_id reaches default handling block for either, consider this a verifier internal error and fail verification. Otherwise a helper w/ poisoned btf_id but no verifier logic replacing the type will cause a crash as the invalid pointer is dereferenced. Also move BPF_PTR_POISON to existing include/linux/posion.h header and remove unnecessary shift. [0]: lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com [1]: lore.kernel.org/bpf/20220904204145.3089-1-memxor@gmail.com Signed-off-by: Dave Marchevsky Acked-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20220912154544.1398199-1-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov --- include/linux/poison.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/poison.h b/include/linux/poison.h index d62ef5a6b4e9..2d3249eb0e62 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -81,4 +81,7 @@ /********** net/core/page_pool.c **********/ #define PP_SIGNATURE (0x40 + POISON_POINTER_DELTA) +/********** kernel/bpf/ **********/ +#define BPF_PTR_POISON ((void *)(0xeB9FUL + POISON_POINTER_DELTA)) + #endif -- cgit v1.2.3-59-g8ed1b