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([2600:1700:6cf8:1240:2ccf:8565:88c4:147c]) by smtp.gmail.com with ESMTPSA id 3f1490d57ef6-e0ec8be5ab0sm1552156276.17.2024.08.13.09.52.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Aug 2024 09:52:27 -0700 (PDT) Message-ID: <00ec1572-9f74-4a01-b30a-4eb03489284e@gmail.com> Date: Tue, 13 Aug 2024 09:52:25 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC bpf-next 2/5] bpf: Handle BPF_KPTR_USER in verifier. To: Alexei Starovoitov , Kui-Feng Lee Cc: bpf , Alexei Starovoitov , Martin KaFai Lau , Song Liu , Kernel Team , Andrii Nakryiko , Kui-Feng Lee References: <20240807235755.1435806-1-thinker.li@gmail.com> <20240807235755.1435806-3-thinker.li@gmail.com> Content-Language: en-US From: Kui-Feng Lee In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/12/24 09:48, Alexei Starovoitov wrote: > On Wed, Aug 7, 2024 at 4:58 PM Kui-Feng Lee 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 >> --- >> 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?