Commit 257af63d authored Jan 31, 2020 by Alexei Starovoitov Committed by Daniel Borkmann Feb 04, 2020

bpf: Fix modifier skipping logic

Fix the way modifiers are skipped while walking pointers. Otherwise second
level dereferences of 'const struct foo *' will be rejected by the verifier.

Fixes: 9e15db66 ("bpf: Implement accurate raw_tp context access via BTF")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200201000314.261392-1-ast@kernel.org

parent a525b088

kernel/bpf/btf.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -3931,6 +3931,7 @@ again:

		if (btf_type_is_ptr(mtype)) {
		const struct btf_type *stype;
		u32 id;

		if (msize != size \|\| off != moff) {
		bpf_log(log,
		@@ -3939,12 +3940,9 @@ again:
		return -EACCES;
		}

		stype = btf_type_by_id(btf_vmlinux, mtype->type);
		/* skip modifiers */
		while (btf_type_is_modifier(stype))
		stype = btf_type_by_id(btf_vmlinux, stype->type);
		stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id);
		if (btf_type_is_struct(stype)) {
		*next_btf_id = mtype->type;
		*next_btf_id = id;
		return PTR_TO_BTF_ID;
		}
		}