On 8/12/24 09:48, Alexei Starovoitov wrote:
On Wed, Aug 7, 2024 at 4:58 PM Kui-Feng Lee <thinker.li@xxxxxxxxx> wrote:Give PTR_MAYBE_NULL | PTR_UNTRUSTED | MEM_ALLOC | NON_OWN_REF to kptr_user to the memory pointed by it readable and writable. Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx> --- kernel/bpf/verifier.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index df3be12096cf..84647e599595 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5340,6 +5340,10 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, int perm_flags; const char *reg_name = ""; + if (kptr_field->type == BPF_KPTR_USER) + /* BPF programs should not change any user kptr */ + return -EACCES; + if (btf_is_kernel(reg->btf)) { perm_flags = PTR_MAYBE_NULL | PTR_TRUSTED | MEM_RCU; @@ -5483,6 +5487,12 @@ static u32 btf_ld_kptr_type(struct bpf_verifier_env *env, struct btf_field *kptr ret |= NON_OWN_REF; } else { ret |= PTR_UNTRUSTED; + if (kptr_field->type == BPF_KPTR_USER) + /* In oder to access directly from bpf + * programs. NON_OWN_REF make the memory + * writable. Check check_ptr_to_btf_access(). + */ + ret |= MEM_ALLOC | NON_OWN_REF;UNTRUSTED | MEM_ALLOC | NON_OWN_REF ?! That doesn't fit into any of the existing verifier schemes. I cannot make sense of this part. UNTRUSTED | MEM_ALLOC is read only through exceptions logic. The uptr has to be read/write through normal load/store.
I will remove UNTRUSTED and leave MEM_ALLOC and NON_OWN_REF. Does it make sense to you?
