From c67cae551f0df80421b5703ee56ff5e2fe9c4de6 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Fri, 25 Nov 2022 14:06:17 -0800 Subject: bpf: Tighten ptr_to_btf_id checks. The networking programs typically don't require CAP_PERFMON, but through kfuncs like bpf_cast_to_kern_ctx() they can access memory through PTR_TO_BTF_ID. In such case enforce CAP_PERFMON. Also make sure that only GPL programs can access kernel data structures. All kfuncs require GPL already. Also remove allow_ptr_to_map_access. It's the same as allow_ptr_leaks and different name for the same check only causes confusion. Fixes: fd264ca02094 ("bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx") Fixes: 50c6b8a9aea2 ("selftests/bpf: Add a test for btf_type_tag "percpu"") Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20221125220617.26846-1-alexei.starovoitov@gmail.com --- kernel/bpf/verifier.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4e7f1d085e53..d0ecc0b18b20 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4703,6 +4703,18 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, u32 btf_id; int ret; + if (!env->allow_ptr_leaks) { + verbose(env, + "'struct %s' access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN\n", + tname); + return -EPERM; + } + if (!env->prog->gpl_compatible && btf_is_kernel(reg->btf)) { + verbose(env, + "Cannot access kernel 'struct %s' from non-GPL compatible program\n", + tname); + return -EINVAL; + } if (off < 0) { verbose(env, "R%d is ptr_%s invalid negative access: off=%d\n", @@ -4823,9 +4835,9 @@ static int check_ptr_to_map_access(struct bpf_verifier_env *env, t = btf_type_by_id(btf_vmlinux, *map->ops->map_btf_id); tname = btf_name_by_offset(btf_vmlinux, t->name_off); - if (!env->allow_ptr_to_map_access) { + if (!env->allow_ptr_leaks) { verbose(env, - "%s access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN\n", + "'struct %s' access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN\n", tname); return -EPERM; } @@ -16679,7 +16691,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr) env->allow_ptr_leaks = bpf_allow_ptr_leaks(); env->allow_uninit_stack = bpf_allow_uninit_stack(); - env->allow_ptr_to_map_access = bpf_allow_ptr_to_map_access(); env->bypass_spec_v1 = bpf_bypass_spec_v1(); env->bypass_spec_v4 = bpf_bypass_spec_v4(); env->bpf_capable = bpf_capable(); -- cgit v1.2.3