From: Alexei Starovoitov <ast@xxxxxxxxxx>
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 those programs are GPL if
they access kernel data structures. All kfuncs require GPL anyway.
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")
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/bpf.h | 5 -----
include/linux/bpf_verifier.h | 1 -
kernel/bpf/verifier.c | 17 ++++++++++++++---
3 files changed, 14 insertions(+), 9 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c6aa6912ea16..4235ac4ed1c8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1891,11 +1891,6 @@ static inline bool bpf_allow_uninit_stack(void)
return perfmon_capable();
}
-static inline bool bpf_allow_ptr_to_map_access(void)
-{
- return perfmon_capable();
-}
-
static inline bool bpf_bypass_spec_v1(void)
{
return perfmon_capable();
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c05aa6e1f6f5..b5090e89cb3f 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -531,7 +531,6 @@ struct bpf_verifier_env {
bool explore_alu_limits;
bool allow_ptr_leaks;
bool allow_uninit_stack;
- bool allow_ptr_to_map_access;
bool bpf_capable;
bool bypass_spec_v1;
bool bypass_spec_v4;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6599d25dae38..69040c09f4f5 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;
}
@@ -16675,7 +16687,6 @@ 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();
--
2.30.2
